Just about any holster that is not skin tight form fitted (and maybe even then) that fits 5906/4006 should work with the M59.
Dimensionally, they are not all that different between the 1st gen (M59) and 2nd gen (x59) pistols and the 3rd gen (5606) pistol forward of the grip.
The slides are similar too. A non thumb strap, open top style should adapt nicely.
My preference is a Safariland paddle,
Model 568 , I have used it with both a 2nd Gen 459 and a 3rd Gen 4006. It's adjustable for cant and retention.