Good Morning!
Narrow gauge modeling isn't an obscure end of our hobby...it's just in a different location. To track down suppliers, buy Narrow Gauge & Short Line Gazette magazine. The HOn3 models that I've built are: LaBelle, Rio Grande Models, Grandt Line, Taurus, Quality Craft (Gloor Craft), Rail Line, and a Roundhouse Shay. Flex track, pre-assembled turnouts, detail parts, etc. are all available...but not at Walthers. Narrow gauge modeling is a different field all together and has its own suppliers, magazines, organizations, etc. Check the NMRA website for more info or email me directly. I'd be glad to help. Just now building in Sn3...HOn3 is a bit small for my middle-aged sight. Good luck!
Russ