Greetings!
Seems like I got both of my smaller ones (6-8 inch blades) at yard sales for probably about $5.00 each. These are the ones I use on my heaters, stovetop (with a heat diffuser), or outside powered by a liquid candle. They are also available for under $20 with free shipping on both Amazon & Ebay. Be careful though, some of the listings are for a blade only…
These newer ones appear to use a Peltier chip to generate the power for an electric motor, by converting heat into electrical power.
I also have a much larger antique one, made in 1880 that uses a heat powered stirling engine. I’m hoping to convert it into either a liquid candle powered swamp cooler or full blown air conditioner, and maybe even incorporating heating into the same unit. The ways they accomplished things before electricity, or where it wasn’t available, has always intrigued me, and I think a combination of history and newer technologies would serve us nomads better than much of what many people use today. Simple, safe, effective, reliable, cheap, & easily duplicable are my goals.
I envision the day when my entire rig including all my appliances & amenities are powered by water converted into hydrogen, and I will accomplish it if I live long enough. The technology exists, although mostly hidden, but I believe if I can take bits & pieces from multiple places and combine them, it can be done.
Cheers!