I use a Spotmatic leather case (pebble-grain shoe leather) and it works fine with the Pentax-K 55/1.8. I am very pleased with the case. I found it in the rummage box at a local used camera shop. It looked pretty rough, but the inner lining was in excellent shape. I think I paid about $5. When I got it home, I cleaned it with a little saddle soap and finished off with black Kiwi shoe polish. Looks like new
I showed it to the guy at the shop and the next time I came in, all of their Spotmatic and K1000 bodies were displayed next to newly polished cases! (They had about a dozen of those old Spotmatic cases in various stages of disintegration.)
Steve