You need to find out what action the rifle is built on. It could be a surplus or commerical Mauser 96 or 98, it could also be an FN Mauser action, a 1640, or 1900 (unlikely). Once you find that out it should be fairly easy finding a stock.
Post a picture if you are unsure of the action, look for thumb cut outs on the reciever which would be a tell tail sign of a surplus action. There are many stock options including both drop in synthetics or semi inletted wood stocks from a variety of manufacturers.
Cracked and damaged stocks are very common with these rifles and a properly fit stock, and bedding job will prevent this in the future leaving you with a strong, accurate and long lasting rifle.
