I bought one for my sons xs7 in 243 win. directly from Marlin. If I remember right it wasn't really all that expensive. It came with the recoil pad and swivel studs installed. You might ask around, someone on here might just have on for sale.
I have a black synthetic youth stock I'll sell you for $50 shipped. It came on an XS7Y 7mm-08 and is in like new condition. It has the recoil pad and the sling studs on it. I think I payed about $65 for the adult synthetic one I bought to replace it on the 7mm-08.