For what it is worth.PeteM wrote: ↑Wed Jan 15, 2020 3:11 amI've seen Polyvar's with both a separate head and one that's inclinable and built into the upper frame. A picture of your scope might help - there were several versions.
If it is the former, I suspect you could get a Leica/Reichert head from a Microstar or Diastar and find it optically compatible, though likely a slightly smaller field. The binocular versions are pretty cheap.
I checked on one of these and it doesn't seem like a fit, although it would probably work if it could fit. The forward prism diameter is 25 or maybe closer to 26mm in diameter across it's spherical dimension but it's overall dimension is geometrically different than the one pictured from the Polyvar, with the forward prism being cubic, with two corners clipped off so it fits into the circular center tube of the Seidentopf.