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

BEMO 2254 Gbv FREIGHT STOCK CAR Gterwagen NEW BOXED mc
BEMO 2254 Gbv FREIGHT STOCK CAR Gterwagen NEW BOXED mc
$30.01
Time Remaining: 2d 19h 45m
Buy It Now for only: $30.01
Bachmann Spectrum On30 Stock Car Painted In Lettered 27599
Bachmann Spectrum On30 Stock Car Painted In Lettered 27599
$40.00
Time Remaining: 3d 22h 26m

Other On30 Scale train items recently purchased through this site:

Bachmann Spectrum On30 Stock Car Painted In Lettered 27599
BEMO 2254 Gbv FREIGHT STOCK CAR Gterwagen NEW BOXED mc