I spent a couple of hours "forging" this for my middle son's musket.
I used only the highest quality PVC pipe, holding the socket to the bayonet with super glue and a couple of finishing nails to act as pins. Shaping was done with a bench vise, belt sander, and a heat gun, and finally, it was treated with and undercoat of black, the best quality genuine Krylon "Hammered Metal" paint.
Enjoy!
PS: If you didn't have one of these rifles in your childhood, I'm sorry. You were deprived.