Would a water bath work? What temp to you want, and what is the plus/minus?
110°? That’s hotter than I thought. Aquarium thermostats usually only work to about 95°, but there may be exceptions.
I’ve taken apart quite a few space heaters, and the thermostats are usually just bimetallic contacts that bend as the temperature changes. Besides the usual external knob for adjusting the set point, you can bend the contacts themselves to adjust the range over which the thermostat can be set. Depending on the thermostat you get, you may not even have to do any bending to get in the 110-116° range.
Wire the contacts up to a light bulb under your yoghurt pot (put a switch in the circuit), fill the pot with water, and stick in a thermometer. An hour or two should allow the temp to equilibrate, and you can tweak the knob up or down to get the temp you want, It’ll take a few tries, but once it’s right you shouldn’t ever have to mess with adjusting the thermostat again.
But that’s too easy! They’re also unitaskers, and I’m as bad as Alton Brown wrt unitaskers. Shelf space is at a premium too.
My wife made the first batch today in the crock pot with the mason jar bands under the pot - it came out fine. We’ll probably just stick with doing it this way, unless I can keep it in a cooler to maintain temperature. More experimentation in in order.
Back in the day, when oven had pilot lights, my old girlfriend made yogurt in the oven. And we ate a lot of yogurt. We ate in the normal ways, plus just about anywhere you’d use sour cream. I still do.
Me, I’m a gadget guy. give me my machines. 
What’s a “wrt”?
If you are determined to use your crockpot and get tired of using Mason jar bands, look for a remote bulb thermostat with the appropriate range. Mind the stated differential - many are in the 10 °F range - to assure proper controllability. Place the bulb in the crockpot. You will need to find some way of keeping the bulb from direct contact with the yoghurt mixture, like placing it inside a baggie. Then wire the power to your crockpot through the contacts of the thermostat and it will cycle power on and off to maintain the proper temperature.
To keep from ruining the crockpot cord by splicing the thermostat into it, I’d advise wiring the thermostat to control a receptacle, like on an extension cord, and plugging the crockpot into that.
ETA: ps - “wrt” means “with respect to”.
Aha! Thanks.
Greetings,
Though it may be possible to couple a thermostat to a cooker to obtain 40-45°C temperatures, it won’t be even near efficient, and the heating coil may peak at temps higher than your yoghurt bacteria will like.
We used to make quite good yoghurt by setting the pots on the central heating radiator (hot water, 45-55°C more or less) I wonder if an electric blanket would work.
From experience, the cultures just have to be warm (never tested that temperature) even room temp works but takes longer, and elevates the risk of unwanted seed cultures.
Thinking out loud, a cupboard shelf with an inset spotlight underneath may be just right for a try.
I don’t like yoghurt anyway