Dinball's RCMart is where I just picked up a few cans and some thin Neo magnets (Yeah Racing). For coming from Hong Kong, it didn't take that long to get. (2 weeks, standard shipping). For armatures and brushes, I have just been using old stage 1 and 2 motors. At $12 for 4, they're cheap enough to sacrifice.
For winding wire, you can pick up three rolls at Radio Shack for under $5, or you can get bigger rolls from this place:
I'd really like to know where NML or World Champion Engine get their stuff from (especially the nicer armatures), but I'd be willing to bet they won't share that info...
Don't forget to scour the slot car sites, though, as some of the 1/24th and 1/32 cars use 130 motors as well, and some of the parts used in their motors can be scavenged.