Hi Davaa,
Glad you're with us. The new CZ-550 series stock would fit with minor adjustments, take a magazine-less version or a void will appear on each side of the magazine-well. The type of wood which you have is Turkish walnut & unluckely the new CZ riflestocks are made out of the same wood. It has been rumoured that CZ will take American walnut(darker, denser, less patterning in grain) soon. Some of the old stocks were indeed extremely soft to the point of wondering if the wood was'nt suffering of rot.
If Accuraglass from Brownells is'nt available in your area, you can easily take metallic epoxy(aluminum filler) which is very easy to machine afterwards, and is easily cleanable with wood alcool(methyl hydrate/blue liquid used for fondues). Another alternative is Epoxy putty which is much more controlable & cures extremely fast. But a stronger set-up is acquired by Accuraglass due to longer strands of fiberglass.
What animals are you allowed hunting in Mongolia & how's the local hunting laws?
Happy Holydays,
-Fred-