Both molecular sieve and activated carbon are easy to obtain here in UK and US I just dont know how easy it is to obtain in Lithuania. As you are a member of the EU at a guess us in England are closer it would be less shipping and no import duty.
We sent a small oxygen compressor over to Lithuania last week weight was 30 kgs cost £40 shipping by Fedex. If you are looking at importing then its just postage.
As far as the chemicals are concerned we need to know the size of the compressor and ideally the diameter and length of the filter cartridge stack or make and model.
Reason is that with repacking, the chemical used has to be as good if not better than the original stuff. That way the filter lasts as long and the purity is maintained.
Throw away cartridges dont necessarily use the best chemical material as there is little incentive but some critical components of the chemical need to be understood.
To obtain diving quality breathing air the standard in the EU is BS 12021, for other gases with an elevated oxygen concentration over 21% then its BSEN 8478
The mesh size or diameter of the chemical used in your filter is also very important,
The larger the compressor the bigger the mesh size, but filter cartridge diameter and length also is required together with the back pressure setting to obtain purity. This is also known as dwell time
The type of chemical you choose would take up pages to write up correctly needless to say with activated carbon (AC) you must use a granular type made from coconut husks, be careful about using carbon used for water filters and fish tanks or that made from wood.
For Molecular sieve (MS) about the same amount of pages needed but basically it should be 13X angstrom size with the minimum amount or no inert binder (clay silicate) added. Of critical importance is for the EU the chemical must be in steel drums or cans and be in UN certified drums or cans for transport, It should never be stored or shipped in plastic containers unless you are happy with a short shelf life and if customs find and it was shipped air you are in trouble.
Available in UK in 25 ltr steel drums containing about (20kg MS or 10Kg AC)
Also 5ltr steel drums with (4Kg MS or 2Kg AC) or if you want 205 ltr steel drums containing 135Kg MS and 25Kg drums of AC. Iain Middlebrook