You can get CPMI (or is it CMPI?) basepads from Brownells, I use them on my 75's.
Here's the problem:
SP-01 magazines have longer mag tubes and a wraparound basepad. If you use regular CZ-75 extended basepads on those mags, the tubes will stick outbeyond the grip leaving a funny gap before the basepad. It will look like a SP-01 mag in a compact gun. Now you may be able to get the mag sleeve that one sometimes sees for using a full length mag in a compact gun and use that in conjunction with the extended basepad to fill in the funny gap, it will probubly need to be trimmed to the right length.
I don't anticipate there being any commercial manufactured extended basepads made specifically for the SP-01 mags because doing that would make them too long for use in anything other than open division, where an SP-01 is out of place.
