While the 10 round mags from CZ work perfectly, There is the concern that because they are a 2 part mag, and the joining is located up inside the pistol, there is the possibilty that as they wear they could separate and not drop free. Some 10 round mags are constructed so that the forces exerted during a reload are similar to those required to dissassemble the mag. CZ mags do not fall into that category, but the concern continues. Also because the original mag is a full steel body, it may be more durable and resitant to breakage from normal droppage than the half plastic 10 round mags. thirdly, just as a point in fact, the original mags are 19 round mags.
and as another option, tanfoglio mags. I'm playing with their mags, and have ordered some basepads that should match the overall length of the real SP01 mags. This will give me a 10 round mag, with the increased length for ease of reload and the basepad to increase durability. It appears that the Tanfoglio mags are built to a heavier spec than the CZ mags.