I can’t find a Maxxum 50mm f2.
There is a Maxxum 50mm f2.8 macro lens.
You wouldn't .
The only Minolta 50mm f/2 is an old SR mount manual focus lens .
Not an A mount autofocus lens .
If you get one , it won't fit on your camera without an adapter that contains low grade glass , which I wouldn't recommend.
50mm Minolta A mount lenses are 50mm f/1.7 and f/1.4 several versions depending on date produced.
50mm f/2.8 1:1 macro ( several versions) and a 50mm f/3.5 1:2 macro .
Sony also sold a rebadged Minolta 50mm f/1.4 and the 50mm f/2.8 macro .
They also sold a Carl Zeiss 50mm f1.4 SSM lens ( big and heavy , very good quality , not cheap ) and a lens intended for use on APS-C cameras , the 50mm f/1.8 .
The CZ and 1.8 won't auto focus on the Dynax 9xi as one has the built in SSM drive and the other a SAM drive .
People have used it on film and are happy with the results , though you might find it vignettes at large apertures more than the others .
But with the choices available, why bother ?
If you want to see all lens options from all/most makes , go to Dyxum and look up the lens list and reviews for A mount lenses .
Lots of information.