Put him in a room were you can kick the temps up to 80-85. Or you could try this go get a Lamp Fixture and a 50 to 60 Watt regular house bulb from Wal-Mart. Now find a store that sells thin mesh-wire like on a Tank lid. Cut out the plastic area around the rim of your current Bins lid and set the mesh wiring over it. Now just stick the lamp on one of the sides and it will heat your cage up.
Measure the Bins lid before going to get the mesh-wire so you don't have a huge hunk of mesh-wire going over the rim of the bin. Also get a Accurate Indoor/Outdoor Thermometer from Wal-Mart and put that on one side of the Bin and put the probe on the other side of the bin so you can measure the temps and humidity. This is what the Thermometer looks like so you know. I use one myself and it works great.
http://www.songbirdgarden.com/store/...URITE00891.jpg