I'm possibly making too much of this but it caught me completely by surprise and would only be found when the spare is needed.
It appears this size donut spare tire is not available at any of the major tire sources.
My trip to the U-Pullit salvage yard today was to find either a same-sized donut spare or a steel rim to mount a full-size spare for my Daughter's car (got new tires yesterday from Discount Tires; good experience, great price) educated me on old spares. I found a few Saturns with the proper sized spare but they were all in similar condition. A look in an a different 4-lug GM with same sized regular tires found one in good condition. This led me to look in similar cars at their donuts and condition - ALL the Firestone spares in those years were split while the Goodyear ones were not. This Goodyear donut spare is temporary until I get a full size steel wheel (~$70 at Discount Tires) and mount a decent tire or find a source for a new donut tire.
This attached pictures show broken steel belts after dismounting the tire.