This is one that was suggested by our dr office PT person & we like it.
It collects moisture from the air so you get moist heat and you can set time/temp.

here's the Amazon page showing sizes and prices -
http://www.amazon.com/s/?ie=UTF8&key...sl_l4nd1xptp_b

I also got a far infrared heating pad but they are kind of spendy
but the good point is they can penetrate deeper into the tissues- much more then reg heating pads.
http://www.thermotex.com/howworks.htm

general infrared info -
http://www.thmi.com/FIR/heater.html
http://ezinearticles.com/?Far-Infrar...ling&id=788011