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

Westside Model Company HOn3 Narrow Gauge Brass Trucks 1 Pair NOS
Westside Model Company HOn3 Narrow Gauge Brass Trucks 1 Pair NOS
$26.99
Time Remaining: 13d 21h 18m
Buy It Now for only: $26.99
Narrow Gauge and Short Line Gazette Magazine lot of 13 Model Railroad 1979 1981
Narrow Gauge and Short Line Gazette Magazine lot of 13 Model Railroad 1979 1981
$27.99
Time Remaining: 19d 12h 54m
Buy It Now for only: $27.99

Other On30 Scale train items recently purchased through this site:

Narrow Gauge and Short Line Gazette Magazine lot of 13 Model Railroad 1979 1981
Westside Model Company HOn3 Narrow Gauge Brass Trucks 1 Pair NOS