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

HOn3 MINI BOX Unassembled Kit
HOn3 MINI BOX Unassembled Kit
$38.75
Time Remaining: 4d 13h 2m

Other On30 Scale train items recently purchased through this site:

HOn3 MINI BOX Unassembled Kit