In the US, figure on about $60 per TPMS sensor. Here's a site in Canada that has them (but most tire shops probably do too):https://www.gmpartsdepot.ca/p/Chevrolet ... origin=pla
I just went through the same task of shopping for wheels, winter tires, and sensors for my EV. We're selling my wife's BMW 330, and have a set of nearly new Michelin X-Ice tires I was hoping to adapt for the Mercedes. They are 205/50-17 but my EV uses 225/50-17. I bought a set of Mercedes replica wheels on Costco.ca that look fantastic, however they are 8-inches wide, and the spec for those Michelin tires allow for up to 7.5 inches. I then considered taking them back, and finding rims that WOULD work, however I decided saving a few bucks to go with a tire size that the manufacturer doesn't recommend isn't all that smart.
In the end, I went with a set of Pirelli WInter Sottozero 3 tires. Tire Rack has them for the Bolt:
The set cost about $200 more than the Michelins do (for my car), but I wanted more of a performance tire this time around.