I have one for mine, but for some applications I use a padded pouch from Tamrac that's part of a series for modular belt storage. It's about 4x7.5x2 inches with a big velcro flap closure. I can get the Perkeo II (folded, of course) and two rolls of film -- or one roll plus my Digisix meter in the pouch. Of course if you want the "never ready" style case hung from your neck for actual shooting, you'll want the real thing.
I suspect the average camera from the early fifties is more likely surviving than the leather cases of that same vintage. (My 1957 Argus C-3 case is queued up for a major restitching as we e-speak.) You might email Jurgen ("certo6") who sells a lot of folders on ePrey and inquire.
Not a fitted case, but if you want an elegant vintage leather case suitable for any medium format folding tourist camera and a few accessories like a lens shade, filters, small meter, and film, look for a Perrin No. 700 case. I don't have one for sale, but I've owned two, one for a Bessa II that I included when I sold the camera and one for my Perkeo II, which I still have.
Thanks for the suggestions. I do have a Minolta soft pouch that has a belt slot which I mostly use it for my Voigtlander Vito II. The Perkeo does fit in it, but it's a little tight. I did purchase an original Vito II case from KEH, but it is in such good condition that I don't like using it when I'm shooting the Vito II! It's almost like it was never used. I'm planning on e-mailing Jurgen to see if he has a Perkeo case.