I keep VF's in several little cases- My ZM25/28 in a Tiffen pouch that came with a 62mm filter a while back- cordura with a soft lining. Not perfect, but ok. The Rollei 40 VF is in a small jewelry box, again not perfect, but ok. The Pentax 43 VF lives in an old Pentax hood case- leather with a velvet lining- pretty deluxe in it's day I suppose, but the zipper sucks, so yet again not perfect, but ok. I occasionally see old Zeiss VF cases on ebay, but they are always over-priced.
I have a little case coming that might just fit the bill a 7x7cm leather pouch, much like Noel seems to have described above...