I bought this for Jewelina
http://www.puplife.com/dogsupplies/snug.html
and Jaden sleeps with his warming puppy. Its smaller and just has the rice pouch that you heat up and stick in it; I got his at petsmart for really cheap, like 8 bucks.
Also, when its colder here I put warm soft water bottles (like the kind you use for injuries) in pillow cases and put them in their beds so it's nice and warm when they want to lay down during the day.