Supergo has the Ultimate Direction xSpurt hydration pack on sale for $31.98 through 7/24/2003.
Ultimate Direction makes great hydration packs. I have the xSpurt and I really like it. It is very stable. It has an adjustable yoke on the back which lets you adjust it’s placement on your back so it will fit you better than other popular brands. The pack is designed to fit low on your back which is what makes it so stable. You can jump around and hop with the pack on and it won’t jump around too much. The pack has enough room to hold two bladders which can be handy when you’re riding around in Moab on a hot day.
The model Supergo has is an old model. New versions (this year) have a slightly different bladder and a different bite valve. I’ve had no problems with the bladder in mine (no leaks) and the bite valve works just fine.
Highly recommended if you’re looking for a backpack style hydration pack.