For an 18x8.5" wheel with aero covers that DOES fit over the M3P PUP brakes, the "Fast EV" EV01(+) is the only one I've come across. Be sure to get the ET35 version where the size/fitment says "Performance Model 3."
The EV01+ Wheels Designed for Tesla Model 3 by Fast Wheels in Canada. Created to not only look amazing on your Tesla but they are lighter than factory Tesla rims as well as more aerodynamic. Increase range with Fast Wheels EV01 and set your Tesla Model 3 apart from the rest.
www.aftermarketev.com
I've seen a few TMC members post about using them, with pictures, so they seem legit. I think they actually look pretty good on the car too (with aero covers off), even though the design looks overdone when looking at the wheel by itself.
I and many others can tell you from experience though, that pretty much any 18x8.5" wheel will be an efficiency improvement over the M3P Uberturbines. The size and weight difference alone are of real benefit. Aero covers should be extra benefit of course at high speeds, so don't let me talk you out of them.
On the flip side, snow-rated tires tend to have poor efficiency (even in dry weather). So that will probably counter some of your gains from the smaller wheels. Obviously winter tires are not optional for you, I'm just mentioning to set expectations.