Seedling Heating Mats

I want a heating mat to speed up the germination process. I plant seeds and I swear it takes weeks for them to germinate even in this hot hot weather (70 is quite hot here in Renton). I've been looking around but heating mats specifically made for seedlings are just not in my budget. So I'm looking into ways to make my own. I hope I can put together something efficient in less than 10 bucks :)