Belt Tensioner Headache

[TBeegan]

I own a 1990 GTZ. I'm sure that means something to all of you. but for some reason, that means nothing to anyone at autozone or napa. My belt tensioner FLEW off my engine while I was doing about 70mph, after I pulled away from the toll booth. I did not know what I heard under the hood until I got home and saw my serpentine belt was laying in the undercarraige. I then also noticed a hefty spring, which to me, looked pretty important. Upon further inspection, I was surprised to see the tensioner had flown off its mount. Auto zone was quick to find a replacement. It was not the right part. After much digging and frustration, I found a used one inside of a Cutlass at a junk yard! Where can I find a NEW ONE?

[Asylum]

GM number is 24575670. Probably expensive.

rockauto.com has four or five choices.