That shrink tubing idea might just work, if it's walls are thin. Let us know how that works out. Ingenious idea.
As far as I know only the guide rods and recoil springs from the G19's fit the CZ100. The internals are totally different. I got the AroTec guide rod from
Lone Wolf Distributing. Not sure if they still carry them. They change suppliers quite often. Your best bet might be a local gun show. There are usually lots of people with glock parts. Take the 100 to check for fit.
All the parts I have were purchased from CZ-USA. I just called their parts number and told them what I wanted. They had everything on my list.
Good shooting.