IF your shotgun is the Smith & Wesson Eastfield 916, it has been out of production for some time. SOME (not all) parts are available from Numrich- see their website at gunpartscorp. You can also check with local gunsmiths, gun shows, etc.
www.gunstockinc.com
I have a fairly complete selection of parts for this model. repair@countrygunsmith.net
You can purchase parts for a Ranger model 30 16 gauge shotgun at these locations. Gunbroker, Topgunsupply, Budsgunshop, Gunpartshop and Midwayusa.
Numrich gun parts
Try your local gunsmith. The Riverside is a Stevens shotgun. If you can find out which model it is, you can probably find the wood at Numrich Gunparts
Try e-gunparts.com
Yellow pages category = GUNSMITHS.
That should be a Savage/Springfield Model 18. If you can't find parts from a local gunsmith, try http://www.e-gunparts.com i have a sears roebuck bolt action .410 shotgun model 110.1120 3''. i need the shell ejector piece. to get a clip for a shotgun try marlinguns.com.
Where can you find parts for your Charles daily shotgun
numrich gun parts Follow the Related Link at the right
Depending on which parts, they may need to be made.
A FEW parts are available from gunpartscorp website.