Here's a 21" Kona in St. Louis. The Konas I rode from that era had pretty long top tubes so fit kinda big. Might be worth a test ride at least. (EDIT: Ooops, it's aluminum. Nevermind.)

http://stlouis.craigslist.org/bik/2177509581.html

I'm a life-long lover of steel, but since I found my Trek 4000 in the trash, I've found I don't mind aluminum MTBs so much. When you're running 1.5" or bigger tires you don't "feel" the frame so much.

Factor in that you'll generally save 5-10 pounds going with a 1998 MTB over a 1988 MTB of the same level and a newer one might be worth considering also.

IMO MTBs peaked in the mid 90s, for the type of riding I do. They got really light by then, but it was before most of them were designed for long-travel forks, so I like the geometry.