I've got an '80s 1.6TD with AC, it has the alternator driven off the AC compressor via a short belt with an idler pulley. The bearing in mine was toast causing it to rattle and chew up belts. Cost for a new pulley - $65! Seems a bit much...
Well, I found the bearings and grabbed a stash of them. I've replaced mine already using a bench vise and a socket as a press, took maybe 20 minutes and the problem is gone!
The bearings are a sealed ball bearing good for up to 15,000 RPM. They're the same type as the factory ones, meant for the same application.
I've got a bunch of extra bearings - $10 including shipping to anywhere in Canada or the US, or 2 for $15. PM if you're interested...