I get lots of my detailing supplies from Scale Dreams. Rick has flocking, ignition wire, wire looms and other PE items, glue, wheels/tires, and all kinds of great stuff. I've heard some people buy Martha Stewart flocking at Michaels or Hobby Lobby - I never have. Some people buy the pre-wired distributors from Chris Morgan (?) but I use aluminum tubing to make my own or drill out a kit distributor.
I've tried making throttle linkage but just can't my hands to follow my brain with the teeny little parts.
Check some of the other posts and links to suppliers here on the forum. Purchase/subscribe to MCM and look at the suppliers in the mag.