Tough one this, I'm tempted to say go get a gun that fits the lad, but, we are here to help whenever possible!
IF you know someone really clever with a bandsaw, you could remove the buttpad & simply shorten the stock, then buy & fit a new pad (it's gonna be smaller you see) keep the stock offcut, it wouldn't be too difficult to reattach it later, if however the cut isn't 100% tidy, you'd ruin the stock & that's gonna cost in the region of 180 smackers to put straight, if Raj would post a pic of his homemade one, I'd be interested to see how you got round the rear attachment fixings Raj, if it's easy enough then I'd suggest making a shorter stock?
BTW, make sure the bolt isn't an issue if he's a lefty!
Westlake fit for the bin
Webley Raider 10
1st Grand Order member