Shown on page 30 of Packing Iron it is attributed to the San Antonio Arsenal 1885 - 1895. It is described as "experimental, right hand design, often credited to Captain James Ropes of the 8th Cavalry Regiment of Fort Ringgold Texas, incorporates the extended belt loop/back skirt reminiscent of the civilian Mexican loop holster. Constructed of black weight bridal leather, it features a full-flap top with strap and finial closure, ten sewn-in cartridge loops at the mouth of the holster beneath the flap, and an extended blet loop.skirt attached to the holster by a single, riveted strap or loop."
It is intended for a Colt SAA or Schofield revolver. Very unusual, sort of neat, but long after any use of a conversion type revolver by the military. I don't know of any commercial maker offering one, but custom makers such as Rick Bachman or Stan Dolgea would probably make one for you.