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

On30 5 Ton Wooden Hopper Car Prairie Locomotive Works NIB
On30 5 Ton Wooden Hopper Car Prairie Locomotive Works NIB
$39.99
Time Remaining: 9d 10h 20m
Buy It Now for only: $39.99
HALLMARK MODELS HOn3 BRASS EAST BROARD TOP 3 BAY STEEL HOPPER CAR
HALLMARK MODELS HOn3 BRASS EAST BROARD TOP 3 BAY STEEL HOPPER CAR
$74.00
Time Remaining: 15d
Buy It Now for only: $74.00

Other On30 Scale train items recently purchased through this site:

HALLMARK MODELS HOn3 BRASS EAST BROARD TOP 3 BAY STEEL HOPPER CAR
On30 5 Ton Wooden Hopper Car Prairie Locomotive Works NIB