Hi Mike,
The nearest thing I can think of that would meet your criteria would be the Celestron Ultima type EP. I have a 30mm parks GS which I understand is the same EP just re branded. At F6 it is very sharp across most of the field compared to a Plossl. Some astigmatism at the very edge only. 52 degree AFoV. When I get that finderscope of yours
I would be happy to ship the 30mm Parks GS with the return package - on loan - for you to try.
Cheers,