If am not mistaken the 721 and the 700 BDL long action are very similar. It is possible a stock for the 700 might fit. If not, Boyds makes a laminated semi inleted stock for the 721 along with a line of stocks for the 700. I believe Ram-line make a synthetic stock that fits. There are quite a few mfg out there and a google search for the stock might be in order. If your son is that clumsy the synthetic might be in order.