Lots of info on here
http://www.ifish.net/board/forumdisplay.php?f=53&order=descNot many tackle stores keep a full line of parts in stock. I think they would rather sell the finished product. You'll probably need to order.
http://www.pen-tac.com/ Great stuff; expensive.
Same here
http://www.rvrfshr.com/http://www.fishermanshack.net/cart.htmlgood selection; great to deal with.
http://www.jannsnetcraft.com/ Ohio company. Tons of stuff.
http://www.hagensfish.com/ Minnesota. Great deals on bulk quantities.
Search "lure parts" "spinner parts" etc. and you will find tons of suppliers. Local ones will have more of what you're looking for, but will be more spendy. Places around the country will have more items, but less "salmon/steelhead" type stuff; they tend to be less expensive, especially if you buy larger quantities.
I am more concerned with getting quality blades than other parts. The heavier gauge (thicker) blades throw much more vibration and you can feel them through the rod much better to tune that "slow flutter" thump that can be so productive. Quality finishes (silver/gold plate) throw much more flash- which can really make a difference at times. Other times, I think the cheapest nickel plated blades fish just as well. Bodies I'm not too picky about. Hollow core pencil lead works well if you want to go to the trouble of painting. I would recommend getting heavier wires also- I hate bending wires all to heck on fish.
Hope this helps. Good luck.