The CZ vz.52/57 is a late production variant of the CZ 52 rifle, chambered in 7.62x45mm.
The Soviets pressured the manufacturer to make it compliant with the AK round, so the newer rifles were so chambered.
Production of these rifles halted in 1959.
It's going to be tough to find a model in 7.63x39... relatively few were made, and those weren't very accurate or reliable. It was designed for the larger, more powerful cartridge, and the difference in functioning was readily apparent.
You can still find a good CZ 52 in it's original chambering, though... and they work just fine, and ammo is pretty cheap.
Flyer