where do i get these

[homegrone30]

http://www.driveshafts.com/pages/bmw.html

stock driveshaft with new greaseable and replaceable u-joints and new carrier bearing.

I was quoted $450 with a $75 core charge, but that is for a custom length so it should be cheaper for "just" the replacement.

you might try drive shaft king i found them after i bought a rebuilt d-shaft. I believe they quoted me like $450 shipped both ways to make your drive shaft serviceable.
Drive Shaft King

228 Dallas Fort Worth Tpke
Dallas, TX 75208
(214) 941-7122