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

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 22m
Roco 32403 H0e Electric Light Railway Soft Right New Original Packaging
Roco 32403 H0e Electric Light Railway Soft Right New Original Packaging
$34.09
Time Remaining: 1d 15h 46m
Buy It Now for only: $34.09
16 LOG BRONC O On30 Model Railroad Waterline Hull Unpainted Cast Resin Kit FR65
16 LOG BRONC O On30 Model Railroad Waterline Hull Unpainted Cast Resin Kit FR65
$29.95
Time Remaining: 2d 10h
Buy It Now for only: $29.95
HAWTHORNE VILLAGE MASTERPIECE RAILWAYS THOMAS KINKADES CHRISTMAS EXPRESS ON30
HAWTHORNE VILLAGE MASTERPIECE RAILWAYS THOMAS KINKADES CHRISTMAS EXPRESS ON30
$100.00
Time Remaining: 5d 8h
Buy It Now for only: $175.00
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 51m
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
86 HOWE TRUSS DECK BRIDGE S On30 Model Railroad Structure Craftsman Kit HL109S
86 HOWE TRUSS DECK BRIDGE S On30 Model Railroad Structure Craftsman Kit HL109S
$174.95
Time Remaining: 11d 12h 43m
Buy It Now for only: $174.95
g Bachmann On 30 BOXED 26114 Combine Cars PRR Pennsylvania Railroad
g Bachmann On 30 BOXED 26114 Combine Cars PRR Pennsylvania Railroad
$45.00
Time Remaining: 15d 17h 6m
Buy It Now for only: $45.00
g Bachmann On 30 BOXED 27714 Caboose PRR Pennsylvania Railroad
g Bachmann On 30 BOXED 27714 Caboose PRR Pennsylvania Railroad
$30.00
Time Remaining: 15d 17h 9m
Buy It Now for only: $30.00
Busch 12012 H0f Field Railway Field Railway Start Set Timber Transport
Busch 12012 H0f Field Railway Field Railway Start Set Timber Transport
$202.65
Time Remaining: 17d 1h 41m
Buy It Now for only: $202.65
On18 Brookville locomotive Conversion kit by Railway Recollections Not On30
On18 Brookville locomotive Conversion kit by Railway Recollections Not On30
$26.77
Time Remaining: 20d 4h 20m
Buy It Now for only: $26.77
O On30 24 WATERLINE LOGS Model Railroad Scenery Unpainted Resin Details FR1665
O On30 24 WATERLINE LOGS Model Railroad Scenery Unpainted Resin Details FR1665
$26.95
Time Remaining: 22d 13h 13m
Buy It Now for only: $26.95
On30 Scale Ultimate Railroad Prototype Picture CD Collection Set 25000+ images
On30 Scale Ultimate Railroad Prototype Picture CD Collection Set 25000+ images
$99.99
Time Remaining: 22d 23h 57m
Buy It Now for only: $99.99
170 HOWE TRUSS DECK BRIDGE S On30 Model Railroad Structure Unpainted Kit HL110S
170 HOWE TRUSS DECK BRIDGE S On30 Model Railroad Structure Unpainted Kit HL110S
$289.95
Time Remaining: 23d 7h 54m
Buy It Now for only: $289.95
Roco H0E 32403 Vineyard Track Light Railway Soft Right 24 Electric NEW + Box
Roco H0E 32403 Vineyard Track Light Railway Soft Right 24 Electric NEW + Box
$34.96
Time Remaining: 24d 2h 3m
Buy It Now for only: $34.96
Roco H0E 32201 s Light Railway Flex Track Length 28 3 4in 12 Pieces
Roco H0E 32201 s Light Railway Flex Track Length 28 3 4in 12 Pieces
$87.58
Time Remaining: 24d 2h 3m
Buy It Now for only: $87.58
Roco H0E 32401 Vineyard Track Light Railway Soft Left 24 Electric NEW + Box
Roco H0E 32401 Vineyard Track Light Railway Soft Left 24 Electric NEW + Box
$34.96
Time Remaining: 24d 2h 3m
Buy It Now for only: $34.96
Busch 12342 Railroad Track Right 2 5 8In R  6 7 8In 225 H0F NEW
Busch 12342 Railroad Track Right 2 5 8In R 6 7 8In 225 H0F NEW
$31.45
Time Remaining: 24d 10h 41m
Buy It Now for only: $31.45
Busch 12339 eimerkettenbagger  BUSCH FIELD RAILWAY Kit HO HOF NEW
Busch 12339 eimerkettenbagger BUSCH FIELD RAILWAY Kit HO HOF NEW
$57.67
Time Remaining: 26d 2h 48m
Buy It Now for only: $57.67
Busch HOF 12342 Railroad Track Right  NEW ORIGINAL PACKAGING
Busch HOF 12342 Railroad Track Right NEW ORIGINAL PACKAGING
$30.56
Time Remaining: 27d 4h 5m
Buy It Now for only: $30.56

Other On30 Scale train items recently purchased through this site:

Roco 32401 Narrow Gauge H0E Electric Light Railway Soft Left
Roy C Link Industrial Narrow Gauge Handbook 7mm O 14 model railways RARE 
HAWTHORNE VILLAGE MASTERPIECE RAILWAYS THOMAS KINKADES CHRISTMAS EXPRESS ON30
On30 Scale Ultimate Railroad Prototype Picture CD Collection Set 25000+ images
Noch 58671 HOM Hoe Rhne Viaduct for Narrow Gauge Railway NIP
170 HOWE TRUSS DECK BRIDGE S On30 Model Railroad Structure Unpainted Kit HL110S
86 HOWE TRUSS DECK BRIDGE S On30 Model Railroad Structure Craftsman Kit HL109S
16 LOG BRONC O On30 Model Railroad Waterline Hull Unpainted Cast Resin Kit FR65
Noch 58668 HOM Hoe bruchstein viadukt for Narrow Gauge Railway NIP
O On30 24 WATERLINE LOGS Model Railroad Scenery Unpainted Resin Details FR1665
On18 Brookville locomotive Conversion kit by Railway Recollections Not On30
Busch 12012 H0f Field Railway Field Railway Start Set Timber Transport
Roco H0E 32201 s Light Railway Flex Track Length 28 3 4in 12 Pieces
Roco 32403 H0e Electric Light Railway Soft Right New Original Packaging
Busch HOF 12342 Railroad Track Right NEW ORIGINAL PACKAGING
g Bachmann On 30 BOXED 27714 Caboose PRR Pennsylvania Railroad
g Bachmann On 30 BOXED 26114 Combine Cars PRR Pennsylvania Railroad
Busch 12339 eimerkettenbagger BUSCH FIELD RAILWAY Kit HO HOF NEW
Roco H0E 32401 Vineyard Track Light Railway Soft Left 24 Electric NEW + Box
Roco H0E 32403 Vineyard Track Light Railway Soft Right 24 Electric NEW + Box
Busch 12342 Railroad Track Right 2 5 8In R 6 7 8In 225 H0F NEW