Shockwave Technologies makes a birdshead-type grip for the Remington 870 shotgun called the Raptor Grip.  The grip is polymer and replaces a standard 870 stock in just a few minutes.  If you’ve never swapped the stock on an 870, don’t worry – it is dead simple to do.

According to Shockwave Technologies, the 870 grip will fit:

• Remington 870 12-gauge firearms
• Remington 870 20-gauge firearms (those built on the larger 12-gauge receiver)
• New England Firearms (NEF) Pardner Pump Protector 12-gauge
• Harrington & Richardson (H&R) Pardner Pump Protector 12-gauge
• Interstate Arms Corp (IAC) Hawk Model 98, 982 and 981R

The site shows the grip is currently selling for $26.99 plus $4 shipping.