If you were to install a remote oil filter, and/or an oil cooler, it would be easy enough to get a temperature sending unit in line with the flow of oil leaving the engine's oil galleys.
Alternatively, you could modify a stock oil pan drain plug, by drilling and tapping it, placing the sending unit there. I'd just be leery of the low-dnagling wiring becoming instantly attached to an immovable object...
I don't have an oil temperature gauge at present__did have one in the past, but didn't want to modify another facia__but I do run a thermostatically controlled oil cooler, and a remotely mounted spin-on oil filter.
Some of the pictures are here, though I know there are some newer ones somewhere, showing the thermostat (with about 45,000 pictures online, I don't remember them all...).