I'm talking about the lower "flat" idler pulley down by the alternator, the one with the impossible-to-find bearing. I have 3 cars needing this repair, so I thought I'd try to figure out something - and I did!!
The original bearing is 40mm OD x 10mm ID x 12mm thick. These bearings are unobtainable. However, I did find a readily-available bearing sized 40mm OD x 17mm ID x 12mm thick (China-made; but seem OK). So I just needed to do something with the ID. I found an easy-to-find "Idler Pulley Reducer Bushing" at various mower supply places that goes from 17mm down to 12mm, and is 12mm thick . Getting closer. I then found another reducer that goes from 12mm down to 10mm, and is also 12mm thick (found these cheap on Ebay). So, I pressed all this stuff together, and pressed it into the old pulley, and I now have a usable lower idler pulley!!
If anyone needs one of these bearing setups, I bought extras (10 bearings, and bushing sets). It was cheaper to buy mass quantities than to just buy the 3 I needed. Figure about $8 each plus postage if anyone wants one.