It would help to know whatmodel of gun it is for stock availability.
www.boydboys.com is a good place to look for replacement stocks. Any half decent gunsmith will be able to cut a stock down if you dont feel comfortable doing it your self.
You can also search the net for youth stocks for a Rem model 7 or 700 or whatever it is and prob have good luck if its either one of those 2 models. Also check Ebay for youth stocks just make sure you get the correct model# for a short action gun.
If you post the exact gun you'll prob get the exact place to get onel