At gun shops, gun shows, on line auctions, e-gunparts, want ads, for sale ads, estate sales, etc.
See related links.
They are available from Numrich thru their website (gunpartscorp) look under Savage- they own the Springfield brand.
A Savage model 340 3-round 30-30 magazine will work for the 842. Check with Numrich-----845-679-2417
E-gunparts.com
Numrich gun parts, part # 198420. $31.80
You should find a Savage model 99 lever action rifle selling for between 350-650 dollars,depending on overall condition,and what caliber it is chambered in.
hoosiergunworks.com Listed under Savage $20.00
The Revelation Rifle marketed by Western Auto Stores in .222 Rem is essentially a Savage 340. Clips are sold by Brownells.com for $30.99 plus shipping
Made by Savage. We have parts. gunshop@nctv.com
You can find a magazine for Savage/Springfield Mod 18C-410 Ga at e-gunparts.com, then NUMRICH iten number229930A and they cost $37.10
Try www.ammoclip.com or e-gunparts.com
Savage sells new 5 and 10 round mags but the back edge will need to be filed down a bit to fit easily