The Mec-Gar aftermarket mags, generally available from CDNN and a few others places, are better-priced than CZ factory mags -- and comparable quality.
Mec-Gar makes the OEM CZ mags for most of their new guns, to CZ's specs, so the Mec-Gar-branded mags are similar, but not always identical. Tanfoglio mags work well, too. I've even picked up some RAMLINE-made Magnum Research mags for the Baby Eagle [that had coil springs attached to the follower with a rivet] for $5 each that worked beautifully -- the springs just couldn't be replaced You should have no problem finding suitable, hi-cap mags for the CZ.
Pro-Mag also made a number of CZ mags over the years, again to CZ's specs -- and they worked beautifully. I think some of the 10-rounds that came with the guns during the "ban" were made by Pro-Mag. Nowadays, however, the only Pro-Mags worth trying in a CZ are the mags for the Compact Models, which are as good as the factory mags, and much, much less expensive. I also bought some of the 10-round CZ factory mags several years ago from CDNN for use in IDPA, and was surprised to see they were Pro-Mags; the only way you could tell they were made by Pro-Mag was in the paper insert in the package they came wrapped in.