Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:5407494.
The original is too loose and can easily be unplugged when I tried. The gap between the car allows it to wiggle enough to unlock, even with the 8mm deeper design.
This is redesigned from scratch and seems to hold well. It includes the thinner latch ring area, a request on the original, and the Tesla logo.
Comment if it works better for you, or if you have any other ideas. I've tried it on ChargePoint, Clipper Creek and Tesla HPWC J1772 chargers.
By request, I uploaded a model that is a tight fit, which is intended to stay on the adapter semi-permanantly. It's a very tight fit.
Note: This works only on Model 3 / Y adapter with no flange. If you have the flange adapter for Model S / X, use my universal design.