I had the lovely "death rattle" coming from my alternator idler pulley... My motor is an A2 1.6TD with an AC compressor so it's got the alternator being driven off of the AC compressor pulley.
The thing was really getting to me, but the only place I'd been able to find a replacement was like $65 for a stupid pulley. I mean, come on!!
Saw elsewhere that the bearing in there was actually fairly common - it's a "6202 2RS" which is a common bearing used in electric motors. Well, I managed to find a sack of them online for cheap!
Replaced mine today using a socket and a bench vise as a press - worked great. I found a socket about the same diameter as the outer part of the bearing and used it like a drift to press the bearing out the other side. Used the same socket to press the new bearing back in (hint: your injector socket is about the right size!) Took me about 15 minutes all told...
I now have a nice QUIET alternator idler pulley, and a bunch of spare bearings if anyone needs one.