They are a weak link, but not total junk. Some of us are still using the stock system for over ten years. My stock CD changer worked perfect for 2.5 years, then jammed, and I got it replaced under warranty. Since that time, I only use one disc at a time to reduce the workload and chance of problems. It's worked great for eight years now.
You can search for a new or used unit-
Isuzu part # 2-90101-826-0.
GM part # 97720069.
Fujitsu Ten Limited part # 113001-5070C151. They made the unit.
Getting a used one from a private owner is very risky. It may have been abused and will not work at all or will not work for long. Some are willing to give it away for just the cost of shipping. Many of the companies selling refurbished units are not trustworthy.
There have been posts about a single disc direct fit plug n' play unit for Isuzu's. However, no one has tried that route yet. Search for 'Isuzu single disc cd player'.
Here's an option, but beware. Research the company. You may get a beautiful new unit that fits and works perfect, or you could get a beat up refurbished player that doesn't even fit.
http://www.oemautosound.com/pc-91-61-isuzu-indash-single-cd-player-1998-to-2003.aspx
That's a nice price, if it's new and the wire harness matches ours and it mounts the same. Again, I don't recall anyone trying this, so it's a gamble.
Mark Griffin