Where to buy Heating Blanket

Hey!

I'm wondering where I can purchase an electric heating blanket around central Tokyo?
I want to do this as I believe it'll be more economical during cold nights than leaving the A/C unit on heat setting for hours...also if anyone has an idea of what price I should expect (single-bed size), it would be great to hear!

Thanks for your time and help!

Any furniture/home goods store should have them (Nittori and Cainz are popular in my area of Kanto for example), but be careful when buying... many have warnings about leaving them on all night.

If you are having trouble finding one like that or are open to other suggestions, in my very cold house I do a few different things to keep warm at night, none of which involve the AC! First off, I have a kerosene heater that I use to heat the room before I go to bed. I also use utampo (heated hot water bottle) at the end of my bed sometimes. Or, I use a futon heater to heat up the futon before I get in... it feels heavenly after that! A friend of mine also put her futon on a hot carpet and turned it on when she came home. By the time she was ready to go to bed, she could turn it off and the heat would have soaked up through her futon. I would be careful about this option though; like with using the electric blanket you should make sure you are around just in case.

Finally to hold heat in, the same home stores often have a lot of options such as insulation for the bottoms of your windows and doors that could help hold head in during winter.

Anyway, when you are looking for a blanket, look around at other options too! Most people don't use only one way of staying warm in the winter, and there are a lot of unique and interesting ways to prevent turning into an icicle in your own home.

I bought cheap one that made by yamazen at rakuten.
http://goo.gl/2prGJ
Now supermarkets, HomeCenters (ItoYokado, Seiyu or TokyuHands and so on) sell them.
In central Tokyo, electrical appliance stores like YodobashiCamera?

As scarreddragon said, heat insulator for windows, hot carpet and so on are efficient and reasonable.

Some Japanese houses are not good at keeping heat for anti-humidity and earthquake-resistant by tradition.(x_x;