Hello Charlie, I've ordered them from:
Whittle Toy Company
24 Front Street
Valley Park, Mo 63088
1-314-821-8771
www.woodentrain.com
This guy makes an extensive line of wooden trains and will happily sell you
wheels, axles, magnets etc. Go on his web site and email or call for prices.
There are also several great web sites with tips and even patterns for making
your own wooden trains. You can even make your own track these days and
there are companies selling the wooden stock and the special router bits. Just
do a Yahoo search using "whittle, magnets, wheels, wooden trains" and you'll
come up with all these sites. I'm sure you know this, but just in case: Be
careful what length cars you make--if you go much above the standard length
of a Brio or Thomas you have to use wheel trucks (not straight axled wheels)
or you'll never negotiate the curves. When I was making them I always had
various Thomas cars on the work bench to use as reminders re: length. Same
goes with height; you'd be surprised at how low the various tunnels, engine
sheds etc. can be and you don't want to make cars that are going to get hung
up.