For the OP's information, Stan Chen is $1k to get on the list and has a long wait. I have no idea how long Jason Burton's list is.
My suggestion is to buy off the rack as close as you can get to what you want. Then shoot it for a year and see if you really want a more expensive pistol. There is good advice above on MIM parts, and you should know that replacing them isn't a plug and play deal.
My favorite ambi safety is the King's Gun Works style. Here is an Ed Brown version https://www.brownells.com/handgun-pa...nt=087-954-001