My problem is, when the metal shaft (Not the impeller) comes loose out of the motor housing, so even with the impeller still in, the shaft wiggles, so the impeller itself does not circulate properly, but gets "stuck" - know what I mean?
Just go and get the replacement shaft and rotor assembly from your LFS. If they dont carry or cant get, try Amazon, or go to the MFG.
You can go to a metal supply shop and get the stainless steel rod. You can get titanium as well as tungsten carbide. What ever you do, the bushings that hold the shaft in place are what will keep the assembly from wobbling and if you lost those, then you will need to get creative. I have used airline tubing.