Gunshops, gunshows, and you might try Numrich at gunpartscorp.
Does not exist. You might find a magazine at egunparts.
Have you tried a web search? Local Library? Do a web search on Harrington and Richardson Books and you will find some sources.
Want ads, gun shows, gun shops, e-gunparts.com
Your harrington and richardson model 900 was made between the years 1962-1973.
Gun shops, guns shows, pawn shops, want ads, e-gunparts.com
Need more information. I Cannot find a reference to an H&R Model 25 bolt action rifle
I find no Harrington & Richardson S/S shotgun manufactured since 1885.
Cornell Publications
Try e-gunparts.com
Blue Book of Gun Values
The Harrington & Richardson 349 Gamester shotgun does not use a clip. It has a tube type magazine that is a pemanent part of the gun, loaded by sliding shells in from the bittom of the gun.
http://www.e-gunparts.com/productschem.asp?chrMasterModel=1560z949