The drawing board is still the buy a replacement fan which isn't a bad option. You just extend the neutral wire with a 1 pin connector so you can wrap it around the sensor. I'd also wrap the sensor with some Kapton tape. It can withstand 200 C easy and remove with no residue.
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The other part of the process involves connecting the sensor to "the wall" Take a look here
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0CCwQFjAC&url=https://www.dalroad.co.uk/wp-content/uploads/2014/06/ampsealedconnectors.pdf&ei=qdlpVZrbOMHRsAXkwoPQDQ&usg=AFQjCNG8Zt_pzLZEnQxGlW_ejZyzJo2Shg starting on PDF page 32. Look through series 11.
Somewhat thinking of the corrogated tube over fiberglass sleaving over Teflon insulated wire. I'll be first to admit overkill, but I can't see any issues with that construction.
I don't think you need sealed connectors, but the corrugated backshells should fit the non-sealed versions.
The unsealed size 11 right angle adapters will extend about 2" (guessing) and that may be a bit much. Digikey has the unsealed versions.
Mouser.com had the right angle backshells for at least one of the the corrogated versions. I didn't quite have the time to compute the clearance needed for the smaller version and estimated the series one version. Nor do I know how much clearance you have to mount a right angle backshell/connector.
These connectors (unsealed anyway) are easy to work with.
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Dimensions and clearances get to to be a pain.
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The next issue is to be able mount the magnecraft relay which I think is a good choice. It's finger safe and a small 40 VA energy limited transformer in some sort of "flush mounted" box. All wiring in the box should be rated for 300 V and the connector COULD go on it's lid. It doesn't have to because it's rated at 24 VAC. You could put a freehanging version in a pocket.
A NEMA rated enclosure with a clear lid might make everyone happy. e.g.
https://www.polycase.com/ml-series Mount it in a recess.
Remember I'm just bouncing ideas.