A viable option might be to just buy a replacement stock. If it's a production gun from Browning or Beretta or Remington or ???, wood is always available if you look around. If it's a Brit classic or an American SxS clunker, you should probably start with the Silvers repro, available in 1" and 1.5". Even if it's an older gun, there is usually wood around.

What is it?