I thought that they were available in 45, but I may be dreaming. I never oaid much attention, cause I have a pair of NMVs in 45, great guns. I ordered a set of 38/357s for my wife who is just starting out. I would have prefered her to us a light load to start in my 44/40s or 45s, but they don't allow new shooters to use calibres over 38s here. I don't know how long you have to be shooting before you can get a pair of big suckers.
I am a confused old cowboy, I have a pair of USAF 44Specials, a pair of Pietta 44WCFs, a pair of NMVs in 45 and a pair of ROAs! The USAFs are sweet and awesome to look at, the Piettas are tuned and are actually the best of the lot to use, apart from being a bit squeezy in the trigger guard (same as the USAFs), the NMVs are great big old girls and have a larger trigger guard, and the ROAs are just plain old spectacular!!!!
Life would be easier if I just settled for teh 38s, but heck! I ain't fast, but I sure am noisy!