As far as the Mosins go I can usually find your basic 91/30s locally, but for the hex receivers, the M44, or my current must have M38 they're likely have to be found on-line. Aim Surplus is my go-to when I'm keeping an eye out. Gunbroker can be a good resource as well, but you have to be careful because folks' asking prices tend to be pretty high. Evert once in a while you can get lucky though. Is there a particular model you're looking for?