Whhewwwww man..............I just went through this !! The only place I saw on the net is either Beretta or tjgeneralstore ! But when you look into it you will see that it costs nearly as much to buy a stock as a new gun !!
I decided to buy a new gun and swap stocks ...........then sell off the new gun with my old plastic stock !! But through looking into it I ended up just buying a Sako 75 Grey Wolf NIB. I will say the Sako is outstanding and the quality compared to a Tikka is kinda of jaw dropping IMO !! I had never actually seen one but read many posts about how they were practically the same...........except some plastic parts on the Tikka. I could not disagree more once having one in hand...........they have some similarities and both shoot exceptionally well I am sure (haven't shot the new one yet)..............but the Tikka is not nearly the gun the Sako is !!
For what a new laminate stock for my Tikka would have cost shipped I bought a Sako NIB shipped ..........and when I sell my Tikka for $500....I am out about the same amount of money as if I would have bought a new stock............yet I ended up with a much nicer rifle !!
That's the route I chose !! If you don't do something like that .............I would buy a new wood stock Tikka and sell your synthetic stock one !! Just my .02$ !!