Many HOn3 products are available through any store that handles Wathers orders. I use my favorite discount LHS for that type of thing, which is a lot. He handles Blackstone, Micro-Trains and everything Walthers distributes.
HOn3 can be a bit tricky finding many items, though. The famous online auction site is a source for out of production stuff, if you're careful not to overbid. More common items will come up again regularly if you search under "HOn3" so there's usually no need to get into the "gotta have it" mode in bidding. Some of the rarer stuff can take some time to reappear, but after you've been looking a year or so regularly, you'll come across most things that were ever available at least once.
Caboose Hobbies has a good selection and good service, in the few times that I've needed them -- just google for their contact info. Coronado Scale Models in Phoenix, AZ is a narrowgauge specialist shop that has a reputation for good service, although I've never used them. Their TX is 602-254-9656 and they really didn't do the whole internet/email thing until recently, from what I've heard, but they do now have an email address -- coronadoscalemod@aol.com
Mike Lehman
Urbana, IL
I am looking for some of your favorite and reliable HOn3 mail order suppliers of locomotives, rolling stock, and supplies, such as track, track joiners, turnouts, etc. I have looked at Blackstone Models and Train & Trooper.
Yours In Model Railroading,
John
Littleton, CO