No other model stock will fit the Model 25. There are house brand versions of the Model 25 and the stock from one of them would fit, some had the same stock and some were without the pistol grip. I would find a good stock repair person and have them add a piece of wood, but I don't know how much is missing. I also always try keep someone from doing a 'restoration' or a refinish - it's OK for old guns to look old. Just get the stock fixed & get it in shooting condition & keep it oiled it so it won't get worse & have fun with it (standard velocity ammo only).

Some house brand's using a Savage Model 25 action -