If you are lucky. Most insurances max out after a month of a cheap ICE rental (~$1,000). You might have to sue to cover the rest.
This only applies if you're at fault. In this case, it's the other party's insurance, and if it takes 6 months to repair it, it takes 6 months. That's what liability insurance is. Of course, they could just total the car too.
I'm not driving a car that ugly!
I'm interested in as I would probably be more likely to replace the car temporarily than sue. But temporarily replacing the car is a lot of time/effort too. And insurance and taxes, etc.
This car can be repaired. Any "replacement" just because you don't want to drive some rental will be out of pocket. You seriously would rather be thousands out of pocket than stare at a dent for a few months?
The other party hit you. You call the insurance company. You tell them that you took the car to a reputable Tesla repair shop nearby, and they need 6 months to repair the car due to parts shortages, and that they want to take the car apart first, then order parts. Tell them that your use case for this car is going skiing, and thus you expect a vehicle with equivalent capabilities as a rental. They'll do one of three things:
1) Find you a shop that can repair the car quicker (this is their job, not yours)
2) Tell you the car is totaled, because $100 a day to rent an equivalent car isn't worth it.
3) Argue with you over the rental.
If the parts are really 6 months out, everyone will be 6 months out. Take the estimate you have and call the closest Tesla service center, and ask for the lead time on the body panel. If it's 6 months, then you're stuck. If it's 4 days, then you know your local place was misleading you and it's probably that they are backed up 6 months.
FYI, there are brand new quarters, on ebay, ready to ship right now.
And in the end, if you sue, you sue your neighbor. You can't sue someone else's insurance company. You sue the person, and the insurance company indemnifies them. So keep that in mind.