We've searched the internet and found the largest collection of On30 Scale trains for sale is on eBay. Below are the listings for 'gauge railroad'.

Roy C Link Industrial Narrow Gauge Handbook 7mm O 14 model railways RARE 
Roy C Link Industrial Narrow Gauge Handbook 7mm O 14 model railways RARE 
$73.07
Time Remaining: 16h 21m
HO Gauge Bachmann White Pass  Yukon Set
HO Gauge Bachmann White Pass Yukon Set
$289.99
Time Remaining: 23h 12m
Buy It Now for only: $289.99
HOn3 Narrow Gauge Durango Press Rio Grande Southern Plow Flanger 02 kit
HOn3 Narrow Gauge Durango Press Rio Grande Southern Plow Flanger 02 kit
$39.99
Time Remaining: 3d 4h 6m
Bachman Spectrum  25127 O gauge Closed Street Car lighted N I B
Bachman Spectrum 25127 O gauge Closed Street Car lighted N I B
$56.00
Time Remaining: 3d 17h 35m
ACCUCRAFT AMS AM39 110 Code 250 6 Switch Narrow Gauge Brass Manual Left
ACCUCRAFT AMS AM39 110 Code 250 6 Switch Narrow Gauge Brass Manual Left
$139.95
Time Remaining: 4d 5h 4m
Buy It Now for only: $139.95
ACCUCRAFT AMS AM39 111 Code 250 6 Switch Narrow Gauge Brass Manual Right
ACCUCRAFT AMS AM39 111 Code 250 6 Switch Narrow Gauge Brass Manual Right
$139.95
Time Remaining: 4d 5h 4m
Buy It Now for only: $139.95
AY100 05 3x Utz Fama AlpinLine Gauge 0 m DC 5251 Gradient running track MINT
AY100 05 3x Utz Fama AlpinLine Gauge 0 m DC 5251 Gradient running track MINT
$25.64
Time Remaining: 4d 6h 45m
Buy It Now for only: $25.64
Roco 32401 Narrow Gauge H0E Electric Light Railway Soft Left
Roco 32401 Narrow Gauge H0E Electric Light Railway Soft Left
$33.85
Time Remaining: 5d 9h 50m
Buy It Now for only: $33.85
Noch 58671 HOM Hoe Rhne Viaduct for Narrow Gauge Railway  NIP
Noch 58671 HOM Hoe Rhne Viaduct for Narrow Gauge Railway NIP
$40.35
Time Remaining: 6d 23h 31m
Buy It Now for only: $40.35
Noch 58668 HOM Hoe bruchstein viadukt for Narrow Gauge Railway  NIP
Noch 58668 HOM Hoe bruchstein viadukt for Narrow Gauge Railway NIP
$53.79
Time Remaining: 6d 23h 31m
Buy It Now for only: $53.79
BINKLEY KIT BUILT HOn3 NARROW GAUGE DENVER RIO GRANDE DRGW BOX CAR WAGON 15 nd
BINKLEY KIT BUILT HOn3 NARROW GAUGE DENVER RIO GRANDE DRGW BOX CAR WAGON 15 nd
$66.01
Time Remaining: 7d 16h 17m
Buy It Now for only: $66.01
Narrow Gauge Cumbres  Toltec 6 CD PHOTO SET 1300 JPEGS
Narrow Gauge Cumbres Toltec 6 CD PHOTO SET 1300 JPEGS
$29.99
Time Remaining: 8d 2h 54m
Buy It Now for only: $29.99
ULRICH O SCALE 1 48 On3 On30 FORD CAB  CHASSIS NARROW GAUGE ALL METAL
ULRICH O SCALE 1 48 On3 On30 FORD CAB CHASSIS NARROW GAUGE ALL METAL
$49.99
Time Remaining: 8d 6h 42m
Buy It Now for only: $49.99
ULRICH O SCALE 1 48 On3 On30 FORD CAB  LOGGING TRAILER NARROW GAUGE ALL METAL
ULRICH O SCALE 1 48 On3 On30 FORD CAB LOGGING TRAILER NARROW GAUGE ALL METAL
$69.99
Time Remaining: 8d 8h 7m
Buy It Now for only: $69.99
BINKLEY KIT BUILT HOn3 NARROW GAUGE DENVER RIO GRANDE DRGW BOX CAR WAGON 315 nd
BINKLEY KIT BUILT HOn3 NARROW GAUGE DENVER RIO GRANDE DRGW BOX CAR WAGON 315 nd
$66.01
Time Remaining: 8d 16h 23m
Buy It Now for only: $66.01
ULRICH O SCALE 1 48 On3 On30 FORD TANDEM CAB  CHASSIS NARROW GAUGE ALL METAL
ULRICH O SCALE 1 48 On3 On30 FORD TANDEM CAB CHASSIS NARROW GAUGE ALL METAL
$52.99
Time Remaining: 9d 5h 1m
Buy It Now for only: $52.99
BINKLEY KIT BUILT HOn3 NARROW GAUGE COLORADO NORTHERN CN ORE WAGON
BINKLEY KIT BUILT HOn3 NARROW GAUGE COLORADO NORTHERN CN ORE WAGON
$132.70
Time Remaining: 9d 11h 37m
Buy It Now for only: $132.70
Lot of 4 Peco SL E1495 Right Hand Turnout Switch Medium HOm 12mm Gauge Scale
Lot of 4 Peco SL E1495 Right Hand Turnout Switch Medium HOm 12mm Gauge Scale
$89.99
Time Remaining: 11d 22h 57m
Buy It Now for only: $89.99
Lot of 4 Peco SL E1496 Left Hand Turnout Switch Medium HOm 12mm Gauge Scale
Lot of 4 Peco SL E1496 Left Hand Turnout Switch Medium HOm 12mm Gauge Scale
$89.99
Time Remaining: 11d 22h 57m
Buy It Now for only: $89.99
ay94 0 5 3X Utz Fama alpinline Gauge 0 M DC 5252 Slope Spout Track MINT
ay94 0 5 3X Utz Fama alpinline Gauge 0 M DC 5252 Slope Spout Track MINT
$25.64
Time Remaining: 13d 13h 29m
Buy It Now for only: $25.64
AY69 05 10 x Utz Fama Roco AlpinLine Gauge 0 m DC 90 5118 5113 Track MINT
AY69 05 10 x Utz Fama Roco AlpinLine Gauge 0 m DC 90 5118 5113 Track MINT
$33.44
Time Remaining: 14d 13h 23m
Buy It Now for only: $33.44

Other On30 Scale train items recently purchased through this site:

Lot of 4 Peco SL E1496 Left Hand Turnout Switch Medium HOm 12mm Gauge Scale
RIO GRANDE Chasing the Narrow Gauge Volumes I II III By Robert W Richardson
Peco LK 555 Narrow Gauge Turntable Turn Table Nickel Silver 0 165 On30 Scale
Box of 12 Peco SL 600 Flexible 36 Flex Track Code 200SM 32 Narrow Gauge Scale
Lot of 4 Peco SL E1495 Right Hand Turnout Switch Medium HOm 12mm Gauge Scale
ACCUCRAFT AMS AM39 110 Code 250 6 Switch Narrow Gauge Brass Manual Left
ACCUCRAFT AMS AM39 111 Code 250 6 Switch Narrow Gauge Brass Manual Right
Peco SL E1487 Streamline Curved Left Hand Turnout Switch HOm 12mm Gauge Scale
Peco SL E1486 Streamline Curved Right Hand Turnout Switch HOm 12mm Gauge Scale
Peco SL E696 Streamline LH Left Hand Turnout Switch SM 32 Narrow Gauge Scale
HO Gauge Bachmann White Pass Yukon Set
Peco SL E695 Streamline RH Right Hand Turnout Switch SM 32 Narrow Gauge Scale
Bachman Spectrum 25127 O gauge Closed Street Car lighted N I B
Narrow Gauge Cumbres Toltec 6 CD PHOTO SET 1300 JPEGS
ULRICH O SCALE 1 48 On3 On30 FORD CAB CHASSIS NARROW GAUGE ALL METAL
Roy C Link Industrial Narrow Gauge Handbook 7mm O 14 model railways RARE 
ULRICH O SCALE 1 48 On3 On30 FORD CAB LOGGING TRAILER NARROW GAUGE ALL METAL
ULRICH O SCALE 1 48 On3 On30 FORD TANDEM CAB CHASSIS NARROW GAUGE ALL METAL
HOn3 Narrow Gauge Durango Press Rio Grande Southern Plow Flanger 02 kit
Noch 58671 HOM Hoe Rhne Viaduct for Narrow Gauge Railway NIP
Roco 32401 Narrow Gauge H0E Electric Light Railway Soft Left
Noch 58668 HOM Hoe bruchstein viadukt for Narrow Gauge Railway NIP
BINKLEY KIT BUILT HOn3 NARROW GAUGE DSPPRR DENVER SOUTH PARK REEFER BOX CAR 606
AY72 05 8x Utz Fama Roco AlpinLine Gauge 0 m DC 90 5117 Compensation pieceW
AY100 05 3x Utz Fama AlpinLine Gauge 0 m DC 5251 Gradient running track MINT