No aftermarket suppliers and they are NOT easy to do. The tolerances for the barrel lug to breach face are not exact enough to reliably expect a proper fit. Barrel fitting can be a DIY job... and if you do search you wil find posts where I have done barrel fitting tutorials. There are no gunsmiths in Canada that do the specific work you are looking for, but most can do it, "if" they want to fiddle their way through the job, but expect to pay a premium... which I would anticipate will be cost prohibitive. Does the cartridge absolutely need to be 9mm Luger and .45 ACP??? H&R produced a number of pistol cartridges... including .357, .44, & .45 Colt... all of these can be converted to long versions, I have done so numerous times.