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'.

QUALITY CRAFT HOn3 East Broadtop Steel Hopper Kit 2 PACK
QUALITY CRAFT HOn3 East Broadtop Steel Hopper Kit 2 PACK
$29.95
Time Remaining: 4d 12h 11m
Buy It Now for only: $29.95
On30 5 Ton Wooden Hopper Car Prairie Locomotive Works NIB
On30 5 Ton Wooden Hopper Car Prairie Locomotive Works NIB
$39.99
Time Remaining: 11d 11h 31m
Buy It Now for only: $39.99

Other On30 Scale train items recently purchased through this site:

QUALITY CRAFT HOn3 East Broadtop Steel Hopper Kit 2 PACK
On30 5 Ton Wooden Hopper Car Prairie Locomotive Works NIB