That's where I got mine. Johnboy had a thread a month or two ago about isopure. Something like "the best tasting protein shake ever!". Do a search on johnboy and I'm sure you'll find it. There were a few replies to that thread listing websites to purchase as I remember.
Now that I've answered your question: why do you want that stuff? I was very dissapointed in mine. The stuff settles out of solution and can't be remixed with just shaking. At least not in my hands. There's an excellent brand called Science Fitness whey protein isolate that tastes very similar to the isopure but doesn't have that problem. I tested it's protein content as well and it tested out at or slightly above label claims too. That's what I use now. Cheaper than isopure too by about ten bucks for a 7 lb tub. PM me if you want more details.
-Spidey