I usually go to SLT for my fans, though I usually also frequent ebay for the harder-to-get fans (Nearly impossible to find a new Nidec VA450DC around here).
SLT will require you to spend quite a fair bit of time searching. Also, some of the shops require a minimum order. Something to think about.
Easiest and most hassle-free is to go online to Performance PCs or Sidewinder and order fans from there.