I’ve cut two leather pancake holsters over the years. Decided that I didn’t need the thumb break retention anymore. So, out came the tin snips from the tool box. Eye balled where I wanted to cut away. Now I got “open top” concealment pancake holsters. No fraying of leather; still still & strong several years later. One was an Aker, the other Gould & Goodrich.
Or a saddle maker. Given that Portland is becoming a wild west town I'm sure they are easy to find.
I’ve trimmed a few leather holsters through the years. Never restitched, but alway made sure to buff and seal the cut edges. I used thinned wood glue for making certain the edges didn’t fray. Was an old school method IIRC was from an old Hal Swiggett article back in the mid-late 80’s.