M10 (metric) cooling fan switch?
 

Previous owner installed a Champion aluminum radiator/fan kit in my K5, but wired the fans to run anytime the ignition is on. I want to change it to work correctly based on tempature, but having a heck of a time finding a temp switch to fit the metric fitting on the radiator.

Near as I can tell, fitting is threaded M10x1.0 straight thread. A 1/8NPT fitting threads in a bit, but obviously there's no taper to properly seal it. Ideally, I'd like to find either a fan controller kit, or even just the fan switch itself to fit the M10, rather than attempting to cut a taper in the fitting with a 1/8NPT tap.

I could have sworn I found a controller kit at Jegs a while ago with a switch threaded M10, but of course I can't find it now. I've just spent several hours digging through the catalogs of Standard Motor, BWD, Echlin, 4 Seasons, etc trying to find something, but it seems that 90% of the listings don't show thread size at all, just vehicle applications.

So, I'm coming to the hive mind to see if anyone has run up against this before....ideally, I'd like to find something with an ON/OFF delta somewhere around 185/195*F, or better yet, an adjustable controller kit, but I'm not completely stuck on those values.