Where do you guys buy thermostats that can control heat mats?

Do they have to be designed for heat mats? Or can you find timer-style thermostats (with probes) that will shut off any electric equipment plugged into it?

Also, somewhat related: if I have heat mats that came with the used tanks I bought, can I rip them off the bottom and stick them on the side, or would that damage them (or even just render them unable to stick anymore). I've never used them because I have substrate in my tanks and because I don't have any safety control in case they over heat, but eventually I'd like to find a way not to keep the whole room as warm during the night as during the day (in the winter time).