No worries... it's a simple DIY project if you're in a pinch. I'm planning on setting up one in that fashion on my frag tank once the main display is up and running.
Whatever system you ultimately choose, I would recommend one which utilizes 2 float switches... one to signal the pump on, and one for a max limit, to signal the pump to shut off if the first switch would happen to fail or stick on.
Also, the Tom's Aquatics Aqualifter pumps make great ATO pumps, and are only around $12.