Buy parts for 410 Stevens model 67 pump shot gun.
I have parts for that model. email@example.com
Check on Numrich gun parts corp website.
Yellow pages category = GUNSMITHS.
Riverside was manufactured by Stevens, so if you can identify the equivalent Stevens model, you should be able to find parts. Check with a local gunsmith.
Numrich Arms should have them.
A FEW parts are available from gunpartscorp website.
Numrich gun parts. Parts availability depends on if you have an old model or new model. There is a nice schematic on their website listed under Stevens 101-7
The 238 is similar to the 258. For parts, try gunpartscorp.com
I would try Numrich gun parts corp.They may be found on the web.
I am not sure about the diagram,but I would check at numrich gun parts corp. first for the parts you need.