How about the simple approach: Get a spare OEM wheel and OEM tire and stick it in the trunk. For most uses, this will be fine. I have never really had much use for a trunk in 30 years (I don't do overnight road trips). But who wants to drive 60-70 miles from home and get a flat tire?
Does Tesla sell one (OEM aero, and OEM Michelin tire)? That's the big "if"! Stick it in a garbage bag - get Styrofoam chunks to hold it in place if you want. If you need a short haul using your trunk, leave the spare at home.
You don't need a jack, wrench, etc. as Tesla roadside or AAA will take care of that for you. But chances are you will not find an OEM tire in a local tire shop - even for an 18" wheel. Whole cost should be $300-$400 for wheel and another $200 for tire. If you have a flat, have the wheel changed and just keep the spare on - using the repaired or replaced old tire as a spare.
Sh1t happens when you least expect it. Take a load off if you can and don't worry about a spare.