I just bought a pump made for a 20-60 Gallon.. It was only like 11 bucks at walmart..
I'm sure you could use a heat pad or something like that.
My enclosure was once a TV amoire that I converted over, so it's rather large. I just put it in a corner and set up a little 'corner room' behind it. I was having some issues with heat once it started cooling down outside, so I put a UV heat lamp outside of the back of the cage, and closed the area off in the corner so the heat didn't escape. This heated up the back wall of the enclosure and raised my ambient temps. So decided to put the pump and water back there so it was a bit warmer also. Seems to help =)