Wanted - Firebird Oem rear disc e brake springs
 

In need of rear disc E brake lever return spring,this spring sits between the apply lever and bracket located on the caliper

I would say if you cant find OE then maybe go with Eldorado springs or Fiero rear caliper springs should work just fine
https://www.ebay.com/itm/333234961637
https://www.ebay.com/itm/265249778527

This may not help you but,, when you buy rebuilt calipers, they come with springs.