As Max had already mentioned, the Hi-Power will fit nicely in a 1911 holster. I carry mine in my Galco crossbreed knock off for my 1911. If you look, I imagine crossbreed makes a lefty holster for the 1911, possibly even one specifically for the Hi-Power. I like the looks and feel of an all leather holster, but I have found that for IWB carry, the Leather/Kydex style holsters are much easier to reholster, and seem to feel a bit thinner.
If you get a quality leather holster it will be made and boned for a high power, no need to settle for one that may work. Don't forget Kramer as well, excellent holsters and if you get the horsehide they are a little thinner than cowhide and tougher.
Good things to know! I have thought about a good (high end) OWB holster for my 1911s, and hi-power. Knowing there is a difference between them in the better quality holsters might just make me buy two. I love my kydex/leather for IWB, but would hate to disrespect J.M.B. buy putting his creations in a plastic holster where everyone could see it.