http://www.bigappleherp.com/Flex-Watt-Heat-Tape
For the price of a cheep electric blanket (minus shipping) you can buy 3ft of the 11inch flexwatt. I'd be afraid of the electric blanket screwing up and burning the house down.
i just bought a heating pad on amazon for 17bucks shipped to my house. i got free shipping bc i'm a prime member but i just thought i would throw that out there for ya. I wouldn't trust a heating blanket. but that is just me.