I also have 3 Eska outboards that need impellers. NOS are crazy expensive but these motors are even older and maybe more plentiful so you can get impellers from China for $12.
Our mfrs, distributors & retailers do it to themselves with their "what the market will bear" pricing.
Edit to add: that $12 chinesium Eska impeller is the same ID and only .006" larger diameter than the Force/Merc.
I'm thinking about giving it a try but the boating season is about over in Michigan.
Barrel season goes on a couple more months. Lol