Military Mauser in .303
According to "Mauser Bolt Rifles" by Ludwig Olson, 3 edition, pg. 179, CZ made a short rifle chambered for the .303 British round that was used in Great Britain for testing ammunition. The book goes on to say that these rifles were also used by Latvia & Estonia. No model is given but it looks like the CZ Model "L" carbine with an extended magazine for the rimmed rounds & no grasping groves on the forend.
Most people have never heard of them & a person would probably have a better chance of being struck by lightning than finding one. Even if one could be found, it would probably cost more than buying a new rifle in whatever caliber you want.
Regards, Hud