Since there appears to be no smaller-cased .25 caliber (such as .257 Roberts) chambered in the CZ, that would be also be chambered in a long action rifle and also have the same case head diameter, it looks like the easiest thing to do to obtain a .25-06 would be to get one in the same cartridge family (such as a .30-06 or .270 Win) and have it rebarrelled to that caliber. This way the action would be the proper length and the feed rails would already be correct for that cartridge case.