I usually get all of mine from Bigals or some other online aquarium retailer (Dr. Fosters & SMith, ThatPetPlace are two more). As you can see, BigAls has about every pin configuration in a variety of different bulbs. http://www.bigalsonline.com/BigAlsUS/ctl3684/cp18367/cl0/powercompactlamps?viewType=CategoryJust wundrin who you all recommend for getting bulbs from: specifically 65w both square and straight pin configs.
thanks in advance
For anything strange and exotic (some sort of weird combination of kelvin ratings), I'm not too sure.