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

Bachmann On30 Scale Train Tank Car Tank Car DS Fire Suppression 27122
Bachmann On30 Scale Train Tank Car Tank Car DS Fire Suppression 27122
$34.46
Time Remaining: 15d 13h 41m
Buy It Now for only: $34.46
On3 On30 WISEMAN MODEL SERVICES WEST SIDE LUMBER CO OIL TANK CAR 5 KIT
On3 On30 WISEMAN MODEL SERVICES WEST SIDE LUMBER CO OIL TANK CAR 5 KIT
$89.95
Time Remaining: 24d 19h 20m
Buy It Now for only: $89.95

Other On30 Scale train items recently purchased through this site:

On3 On30 WISEMAN MODEL SERVICES WEST SIDE LUMBER CO OIL TANK CAR 5 KIT
Bachmann On30 Scale Train Tank Car Tank Car DS Fire Suppression 27122