Diamond Arms Co was a trade name used by Shapleigh Hardware Company of St. Louis, Missouri in the late 19th and early 20th century. It may have actually been manufactured by Iver Johnson, J. Stevens, or one of several Belgian firms. Parts will be hard to find. If you can identify it as a particular IJ or JS, Numrich Gunparts can probably supply them. Otherwise, carry it to all the gunshows within a hundred miles and dig through bins of misc parts.
I can certainly understand wanting to put Grandad's Old Gun back in working condition, but since these store-brand shotguns are not high-dollar collectables and seldom used as shooters, their value (other than sentimental value) is as a decoration. The cost of restoration or repair will probably exceed the gun's cash value.
You can find parts for a 12 gauge Diamond Arms shotgun at several places, including specialty gun shops, online retailers like Brownells or MidwayUSA, and auction sites such as GunBroker. Additionally, you might consider contacting Diamond Arms directly or looking for parts at gun shows. Local gunsmiths may also have access to parts or could help source them.
Go to gunparts.com "Numrich" they have new & used parts
it is a Stevens, parts are interchangeable...
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
Buy my 20 g companion,and there are your parts?wjw2010@live.com
Depending on which parts, they may need to be made.
A FEW parts are available from gunpartscorp website.
Numrich Arms should have them.
Follow the link to the related question.
The 238 is similar to the 258. For parts, try gunpartscorp.com
i found a small list of parts at numrich guns and parts
Parts for a Diamond Arms single shot 16 gauge shotgun can be somewhat challenging to find due to the age and limited production of these firearms. However, various online retailers, gun shows, and specialty shops may offer parts such as hammers, triggers, firing pins, and stocks. Websites like Numrich Gun Parts and Brownells are good starting points for sourcing specific components. Additionally, contacting gunsmiths or local firearm forums may provide leads on where to find the necessary parts.