This will not solve your problem, but thought I would mention it here as we have some first hand experience with this little guy. The screw itself requires a 3mm hex/allen key tool, and it is secured in *MOST* guns using a white colored thread locker. The production line at CZ may be manually applying this thread locking compound to the screw during assembly, this could account for some of the variation that we have seen. Regardless, anyone removing this screw for the first time would be well served to pre-treat the screw threads for a few minutes with some thin penetrating oil from above (can be easily accessed with the lower receiver removed and the hammer cocked back). The penetrating oil will help to lessen the effect of the thread locker and make removing the screw easier... because heat is not a good idea in this case :-)
If the screw does strip out, all is not lost. It is a M4x0.7 screw, approx 10mm in length. You can use a slightly shorter or longer length screw in a pinch. Your local hardware store may have something to get you by until CZ has more in stock. If not, you can order something like this online:
http://www.mcmaster.com/#93070a101/=znl730 .
The factory screw is of course the best option, mainly because it has a nice little shoulder on it that helps correctly locate the screw and sheetmetal trigger case inside of the lower receiver.
So, for good measure, here is a picture of our fun stripping friend: