I buy almost all of my bits from an ebay store. Blackdagger Games.
http://stores.ebay.com/Blackdagger-Games?_rdc=1
I've purchased about $200+ in bits in the past 2 months from him, with excellent service, great price and fast shipping.
You could also check out The WarStore.
http://www.thewarstore.com/
I use them fairly often for certain things. They aren't always the cheapest in town, but sometimes have items that are hard to find elsewhere.