Initially I got an underpowered pump. It also would allow water to pass through, which would empty my water tank! But fortunately I found the right pump on eBay, and it was pretty cheap too:

http://www.ebay.com/itm/281103005575

It's a diaphragm pump, theoretically it can get you 80PSI but don't count on it. It doesn't draw nearly as much power as it says either. But it's just the right size for my purposes!