I will second the nomination of Wolf Ears Equipmen, particularly for a "one off" item ...
In the course of developing my NWMP impression kit, I decided I wanted a Mills-type cartridge belt like the 200 "olive drab" cartridge belts acquired by the Force from Orndorff in 1885, which were the same pattern as a belt then being tried by the US Navy. (Apparently this Navy pattern was suitable for the NWMP because it was made for .50-70 rifle cartridges, so the loops were just right for the NWMP's .45-75 rifle cartridge ... which is effectively a necked-down .50 cal. case.) These belts had loops for .45 calibre revolver cartridges also ... again a good fit for the .450 Adams, .455 Enfield and even .44 Russian cartridges chambered in the various NWMP sidearms.
I got in touch with Stan at Wolf Ears, and he produced the lovely item seen at the bottom of this composite image -
I am nowhere near as slim as the dapper Constable... thus the greater expanse between the buckle and the cartridge loops ...