This particular helmet is the same one used by Polish forces, even the cover is copy of the Polish one. My guess is that they are pretty rare even in Ukraine with most of their soldiers still using the Soviet SSh-68 helmets.
Polish kevlar helmets pop up on the net now and then. The cover you can have made from a combat jacket if you are willing to spend on getting one and pay for the labour.
There's a guy in Moscow that makes custom helmet covers in various patterns, you can try contacting him. Not sure if he speaks English though.
http://kolpak.biz/