If you don't want to try to do double adapters like that, the company EVSEAdapters makes really good 3rd party adapters for the Tesla UMC. They plug right into the electronics box of it and keep the temperature sensor in the plug. Here is the one for an L14-30.
L14-30 Twist-lock Adapter for Tesla™ Model S™/X™/3™ Gen 2 – EVSE Adapters
Well, that’s all sorts of brilliant! Thank you!