What holsters fit a high standard derringer?

None currently make for them.

True, however many holsters were made when these were popular. The two most commonly, and they are rare, common finds are the SAFARILAND Model 52...and GALCO made a nice wallet holster. Sometimes you even find those with slots for 2 extra rounds.

Look on GUNBROKER.com, or EBAY They come up, but expect to pay $30 or more.