Stock
You might have fun on this one. A lot of the Gun industry in Spain is smaller "cottage" type manufacturers, and there is even a variance in the same models that they make. Also, due to the smaller production, not as many guns are available to be parts guns, unlike a North American manufacturer.
If you are really attached to the gun, you should be able to find someone to make you a stock, but it probably will cost you. If this were a top grade shotgun, it would be worth it.
The alternate is to make one yourself. Go to the Library and see if they have a book on stock making, or they can get one on loan from another Library. Walnut is available at better lumber dealers, especially the ones that tend to go for the interior furnishings more. You would be surprised what you can do yourself, if you try. Or, find someone who is a good woodworker near you, and "challenge" his ability.
A better route might be to buy a Blank shotgun buttstock that is already partly shaped. I have even fitted an old rifle stock to a shotgun, after cutting it off to the required length and gluing a bit onto it with epoxy, just to get it operational.
Good Luck
