sold my last one through RSymons - can't recommend them highly enough.
As for buying - I am in exactly the same position, a Tesla 4yr CPO warranty is important to me.
If RSymons could come up with a viable warranty alternative I think their market would be enhanced greatly.
There are a number of warranty firms out there, but I was always concerned about their ability to exclude any defect you actually had, and EVs just sounds like a bunch of excuses from the off.
It's not the Teslas are unreliable, in fact they are as reliable as any cars I have owned and certainly way ahead of Audi and MB in my experience. However if it does go wrong, it is an expensive car so a fix will likely be expensive, and odds on you will lose your car for weeks at the SC. Warranty should improve chances of a loaner you would hope.