Essex Knighty

As his first clay gun, I have bought a Miroku 600 skeet gun for my 5ft 4" 12 year old son, the gun is nice for him with 26" barrels, but the pull is huge at 14-3/4", his right hand is now miles from his face, the pull is much bigger than my Brownings 325, I dont want to butcher this 600 as its a lovely little gun, does anyone have a kids type shorter stock? length around 13-1/2" to 14" that will fit the 600? am Essex & Kent based.