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 train 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 25m
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 13h 1m
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