If the forend is the culprit for not being stiff enough, that can be stiffened by adding some reinforcement. One typical way is to lay piece of carbon arrow in the channel below the barrel(there is usually an open space there). Then fill around it with Accuglass.
If it is the butt, removing the recoil pad a filling the void inside the stock with expanding foam( TuffStuff) will help a little.
Then there is maybe putting a wood stock on it from Boyds. I think you can get one for under a $100 that you would finish.
Putting a $600 stock on it would be like putting croutons on a cow pie.
I'm not recommending anything, just putting options out there.
