recommendations for 12v DC, or USB powered heat mats?

I'm trying to figure out the least electricity-intensive way to keep our prospective/hypothetical corn warm. We have a fairly small solar power setup, so amounts of power matter to us! Also, live in a wood-heated house in Maine and don't stoke the stove at night, so we do need to provide warmth! So: are there any 12v heating pads or USB heating pads that anyone would recommend? Either of these could be wired directly into our system without needing to go through an inverter, which takes more power. But I can't find any reviews or recommendations on any reptile sites for specific brand names. A seller of flexwatt on Amazon told me it can't be wired for DC (12v) only for AC. Would a regular human heating pad work? I'd still put a thermostat onto whatever we bought. Any ideas? If I can't get around this issue then I'm afraid a snake is out for us.
Thanks.

Ah crap, I forgot you left a message for me about this. I wouldn't even know where to look for a solution. I think you might need a bigger audience to ask. There are some seriously handy folks in many of the larger colubrid groups on Facebook. It could be worth asking in, say, Advancing Herpetological Husbandry or Colubrid Crazy. I'm sure someone there has to have some advanced electrical experience.

Don't give up yet. There are a couple solutions, one of which is a 12 volt car seat warmer.
Look on EBay for 12 volt heating pads or seat warmers. The typical size is 16x18 but even if it's a little large you can still use it, as long as you don't crimp the wiring. You would still need to evaluate the heat output and regulate it to an acceptable level. Some of them have a control system. Good luck.

Thanks for the good suggestions and hope. I will keep looking, and finding more people to ask. My daughter and I had a good discussion about corn snakes this morning. She got a bit nervous when I told her they can get as long as I am tall, but she's great. She thought it over a few minutes and said, "I think we just say no to things because we're not used to them. Now I'm used to the idea of a snake as big as you, and I realize that mom's not that tall anyway! I still want to get a snake." Gotta love her.

Don't worry, unless you buy an adult, your daughter will be a teenager before the corn reaches maturity.

To anyone else trying to figure this out- we have a system that is working! I will put together a real post with pics eventually, but just wanted to say you are welcome to be in touch with me if you're looking for information before I get the post up. Yeeha!