Bought a complete ES4500 today on Craig's list for $125. Has been in storage for years but there was no gasoline in the tank thankfully.There are two versions of that engine.
Mine was the older and did not have roller bearings on the rod and it went through the block when it broke, I think I paid $75 for it. The oil looked like tar and it was obvious why it blew.
At the time parts were available for the newer version but that was maybe 17 years ago.
A new project.