First of all, welcome to MCB!
These two websites have tons of information on the VM68: Vm Empire v2.0 www.VM68.com
Palmer's has what you need, I'm sure they will ship to Finland. I know you don't want to order overseas, but this is all there is I believe. VM68 / PMI 3 Seal Kit [SHER061] - $30.00 : Palmers Pursuit Shop!, Where Custom Still Means Something
Another person on this forum also has o-ring kits, American Paintball has them too. Vintage Seal Kits Available