BoogieMan, I just checked Numrich. Looks like they have what you need and a listing the various flavors of 870.
http://www.gunpartscorp.com/Manufac...7896/870-41213/StocksForends-34305.htm?page=5
http://www.gunpartscorp.com/Manufac...7896/870-41213/StocksForends-34305.htm?page=5