2020 Toyota Sienna Visibility & Wipers Problems

In August of 2024, we noticed the drivers side rear view mirror had come loose from it's external housing and was only tethered by wiring that was for mirror movement, defrosting and blind spot awareness. In order for it to be safe to use, we had to duct tape it so that it would not move. Unfortunately, the mirror continues to loosen and has to be retaped frequently. We took it to our dealer (McGovern Toyota) in Portsmouth, NH 0n 23 September 2024 and were told that it could not be fixed but had to be replaced and were quoted an amount of $2025.29 .We were also told that the part was on national backorder and may take a few weeks to arrive. Due to the astonomical cost of replacement, I tried to find other solutions and contacted other dealers and body shops but was told it had to be replaced and could not be fixed. I brought the car into another dealer, nearby (Ira Toyota) in Saco, Maine and they also said it had to be replaced and quoted an amount of $1937.70.I asked them to order the part, which they too, said was in national backorder. I contacted our automobile insurance company (AMICA) who agreed to cover the part and labor and issued a check for $1,420.60. Every month, I would call the dealer and every month I was told that Toyota estimated a delivery within a month, but that month would come and go with no part. For the last several months, I have been in touch with TOYOTA and their "brand engagement advocate" named Julie has reviewed our concern and also has stated that the part will be available by the end of the months of February, March, April, May, June and now July. I have written emails to TOYOTA expressing my dissatisfaction and now have a vehicle which is unsafe to drive due to the instability of the mirror and a vehicle which will not pass inspection (according to the dealer). I feel TOYOTA is lying about the parts actual availability and being disingenuous to what was a loyal customer. I am at a loss what to do next.