Bessa filters do show up occasionally in useable condition, but it took a few years to find original Voitlšnder Bessa II uv, orange & green filters for the wife's pampered & accessorized version II Heliar.

you could establish a daily search in both north america & Europe on the big aution website for Voitlander (or Voitlšnder) 37 mm filter + orange which is same in English & German - eventually you will be lucky.

50/60's B+W push on 37mm glass filters seem to be a similar quality to Voitlšnder but the mounts are not as good but they seem to be slightly more prevalent

best/good luck
alex