Seat Heater

I don't have a brand recommendation,  but I put seat heaters in my wife's Prius and can tell you it is a pretty straightforward process.  Make sure you have a really good set of hog ring plyers if you are going to use hog rings.  Some folks op to use zip ties.  My personal preference is the metal hog rings. I trust them to stay in place whereas I don't have confidence in zip ties to remain strong over time.  I bought the heaters I installed from Amazon and just read a bunch of reviews before I made my choice in brand.  I also watched a few YouTube videos.  If I was able to successfully install the seat heaters, I pretty sure just about anyone can do it.

I have some suitable switches for that, if you're interested. The decals on them have worn a bit, but otherwise they're fine. They're from a Subaru originally, but they're also commonly used in Toyotas. Even the GT86 has them! They have hig and low settings.