https://www.amazon.com/GGG-1133-USP-Flashlight-Adapter-Full-Size/dp/B001BONLOQ
adapts the wonky HK rail to something usable... i think this one is for a light mount... they make them for picatinny and weaver and such.
edit, yeap: https://www.amazon.com/GGG-1133-USP-Flashlight-Adapter-Full-Size/dp/B001BONLOQ