We talked about this about a month ago and I don't know if there were any good solutions. I'm worried about the same thing.
I'm going to sew some pouches on his cage cover and get some big hand warmer things. You can get them 5"x6" size.Then I will put another blanket over it to try to hold in the heat. I've never used them but my son says you can feel the heat coming off the hand and toe warmers about a foot from them.Or you can get those ones they make for your back(supposed to last about 12hrs I think) that might even strap around a small cage. I also thought about hot water bottles(I think I'd put one under and on top)-my neighbor has a gas stove so I can get her to heat water as I need it. Do you have a gas stove?
Here is a heater I found online when I was looking for one for my son's truck. It hooks directly to a car battery so if you had a car battery...only problem would be keeping the battery charged? hmmmhttp://www.sportsimportsltd.com/12dihocehe.html
I'm not sure about using any kind of propane heater, it kind of scares me.
Anyway, any other good ideas out there..I'd be very interested
I hope your power doesn't go out again too. I know some people about 60 miles or so south of us have been without power since Friday's ice storm. We were lucky and got all snow. It's snowing again here now (school is delayed 2 hrs) and they're watching 2 more storms-one on Thurs and one on Sun. Uggggh winter is here! Again!