Fisheye for adaption on Leica M39/Zorki/Fed/Leica M?

[ForenSeil]

Hello
I'm looking for an counterpart of my loved Samyang 8mm Fisheye for new Leica M camera.

I already had the CV 15/4.5, which is very good, but I'm not completly happy with it's "way of distortion" (it's not distortion free and not a fisheye).

I don't care about RF coupling @ </=16mm focal lengths, so adapter solutions would be pleasing. But there are not many other to Leica M adapters and some of them are very expensive.
I know that there are two native Leica M lenses by BelOMA (Peleng 8mm and Zenitar 16mm) but I dislike the circular drawing of the Peleng and the Zenitar has very mixed reputations (inharmonic distortion and fuzzyness due spherical aberration till F11, seems to be best @ F16 ).

Do you have any other suggestions or experiences?
Do you know any ~12-16mm fisheyes which have good price/quality ratio?

My price limit is around 300€ incl. adapter (depends a bit on quality)., the Leitz Fisheye-Elmarit is not an option.