want ads, gun shows, gun shops, e-gunpart.com
Numrich Arms is a good source for gun parts.
If your rifle is a tube magazine type semi auto, it was made under the Revelation brand for Western auto by Savage, and is known as the Model 80. SOME parts may beavailable from a gunsmith, or sources such as gunpartscorp.com. Depending on the parts needed, the cost may be more than the value of the rifle.
Gun shops, gun shows, want ads, e-gunparts.com
Try e-gunparts.com
Your question is too broad to answer- except to say it needs a visit to a gunsmith that can examine your rifle, and see what parts are broken, worn, or loose.
go to e-gun part
Your rifle is a Mossberg 800A. Some parts may be available from Mossberg, some are available for gunpartscorp thru their website, and some may be available thru havlinsales at their website. Good luck!
The Revelation Brand was used by Western Auto for guns made by others, but sold by Western Auto. In the case of your Mdl 104A, this is a Mossberg Model 640 (nice rifle, by the way). Parts may be available thru the website for Havlin Sales, and at gunpartscorp. .
Depending on the part, try Numrich (gunpartscorp) website, or try Mossberg- I think your rifle is a Mossberg 800.
No
Mossberg
Marlin