For my own 3-ds in the back yard, came up with a cheap functional repair.
Dug out the crumbled shot up foam. Wrapped burlap around the body of the target and wrapped with string. Stuck nozzel of insulating foam thru the burlap and filled void. The foam swelled thru the burlap and allowed it to dry-couple days in sun.Cut off excess foam and painted brown. Burlap gave strength to the foam .Has lasted for 2 years am still shooting them. I did not put scoring rings in but am only looking for hunting kill shots. Expense of about eight dollars. Thanks, Roy

Like the burlap idea, Ill try that...Thanks Roy

Thanks for the tip, have to give that a try. Don't want scoring rings anyway.  

I did it without burlap works fine just don't use to much foam!