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

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 20m
Buy It Now for only: $66.01
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 25m
Buy It Now for only: $66.01
HAWTHORNE VILLAGE On30 BACHMANN CONFEDERATE CIVIL WAR J E B STUART B
HAWTHORNE VILLAGE On30 BACHMANN CONFEDERATE CIVIL WAR J E B STUART B
$59.99
Time Remaining: 9d 8h 12m
Buy It Now for only: $59.99
BINKLEY KIT BUILT HOn3 NARROW GAUGE DSPPRR DENVER SOUTH PARK REEFER BOX CAR 605
BINKLEY KIT BUILT HOn3 NARROW GAUGE DSPPRR DENVER SOUTH PARK REEFER BOX CAR 605
$66.01
Time Remaining: 14d 19h 37m
Buy It Now for only: $66.01
BINKLEY KIT BUILT HOn3 NARROW GAUGE DSPPRR DENVER SOUTH PARK REEFER BOX CAR 606
BINKLEY KIT BUILT HOn3 NARROW GAUGE DSPPRR DENVER SOUTH PARK REEFER BOX CAR 606
$66.01
Time Remaining: 19d 22h 1m
Buy It Now for only: $66.01
BINKLEY KIT BUILT HOn3 NARROW GAUGE DSPPRR DENVER SOUTH PARK REEFER BOX CAR 603
BINKLEY KIT BUILT HOn3 NARROW GAUGE DSPPRR DENVER SOUTH PARK REEFER BOX CAR 603
$66.01
Time Remaining: 21d 42m
Buy It Now for only: $66.01
BINKLEY KIT BUILT HOn3 NARROW GAUGE DENVER RIO GRANDE DRGW BOX CAR WAGON 3145 n
BINKLEY KIT BUILT HOn3 NARROW GAUGE DENVER RIO GRANDE DRGW BOX CAR WAGON 3145 n
$66.01
Time Remaining: 21d 16h
Buy It Now for only: $66.01
BACHMANN HAWTHORNE VILLAGE CONFEDERATE EXPRESS NORTHERN LIGHTS BOX CAR
BACHMANN HAWTHORNE VILLAGE CONFEDERATE EXPRESS NORTHERN LIGHTS BOX CAR
$28.00
Time Remaining: 26d 5h 47m
Buy It Now for only: $28.00
BACHMANN HAWTHORNE VILLAGE CONFEDERATE EXPRESS NORTHERN LIGHTS BOX CAR lot 2
BACHMANN HAWTHORNE VILLAGE CONFEDERATE EXPRESS NORTHERN LIGHTS BOX CAR lot 2
$28.00
Time Remaining: 26d 5h 47m
Buy It Now for only: $28.00
BACHMANN HAWTHORNE VILLAGE THE CONFEDERATE GENERAL ROBERT E LEE BOX CAR
BACHMANN HAWTHORNE VILLAGE THE CONFEDERATE GENERAL ROBERT E LEE BOX CAR
$28.00
Time Remaining: 26d 5h 47m
Buy It Now for only: $28.00
New Hawthorne Village Train Dumbos Box Car Disney
New Hawthorne Village Train Dumbos Box Car Disney
$39.99
Time Remaining: 27d 22h 41m
Buy It Now for only: $39.99
On30 Fat Albert Boxcar Conversion to fit Bachmann 18ft flat car
On30 Fat Albert Boxcar Conversion to fit Bachmann 18ft flat car
$37.00
Time Remaining: 28d 2h 13m
Buy It Now for only: $37.00

Other On30 Scale train items recently purchased through this site:

On30 Fat Albert Boxcar Conversion to fit Bachmann 18ft flat car
New Hawthorne Village Train Dumbos Box Car Disney
BACHMANN HAWTHORNE VILLAGE CONFEDERATE EXPRESS NORTHERN LIGHTS BOX CAR
BACHMANN HAWTHORNE VILLAGE THE CONFEDERATE GENERAL ROBERT E LEE BOX CAR
HAWTHORNE VILLAGE On30 BACHMANN CONFEDERATE CIVIL WAR J E B STUART BOX CAR 005
BINKLEY KIT BUILT HOn3 NARROW GAUGE DSPPRR DENVER SOUTH PARK REEFER BOX CAR 606
BINKLEY KIT BUILT HOn3 NARROW GAUGE DSPPRR DENVER SOUTH PARK REEFER BOX CAR 603
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 3145 n
BINKLEY KIT BUILT HOn3 NARROW GAUGE DENVER RIO GRANDE DRGW BOX CAR WAGON 15 nd
BINKLEY KIT BUILT HOn3 NARROW GAUGE DSPPRR DENVER SOUTH PARK REEFER BOX CAR 605
BACHMANN HAWTHORNE VILLAGE CONFEDERATE EXPRESS NORTHERN LIGHTS BOX CAR lot 2