Just my humble opinions:

Tri-Star has moved to w. Broadway in Phx. I was there last week... they might well have a 123 seat you could live with. OK prices but Benz is all they do, and they charge more than a pick-your-part accordingly.

Ecology on 27th av n. of Buckeye is really cheap, but they don't often have MBs. They had a bunch of 116s last I was there in February. Might be worth checking out. I believe any car seat goes for $30 at that place.

The "old German" is actually a Hungarian at All Mercedes Yard (or similar name). Blustery guy (again, IMO)... the Hungarian part is not a slur, he actually will hold forth on how much he hates Germans !!?! in between drinks of Heineken and, in the case of my visit, quoting me $1800 for a set of 15 hole 420SEL chromed wheels. I'm not kidding. Maybe he thought I could afford it?!

I just finished taking apart the 420SEL I bought to part out, I don't have any 123 stuff unfortunately. TriStar isn't too bad, and Ecology is a smokin' deal if they have the car you're after...