I would drill along the stock on each side,so as to put an aluminum tube to bond it to the stock material. One down each side,and glue it back together.Doubt epoxy would adhere to the foam center. Very porous and unlikely to hold. Maybe fit an aluminum rod into both (broke off end and remaining stock) and epoxy the rod in and try using some kind of fiberglass resin to connect the stock at the break. Never know. Could work.