AT AMAZON, save on Emergency Foodstuffs.
UPDATE (FROM GLENN): People have asked me what I think about MREs, freeze-dried food, etc. My thoughts: If you expect just to be hunkered down at home for a while, just stock up on regular food that will keep: Canned goods, pasta, dry beans and rice, even frozen foods unless you expect an immediate power outage when things go bad. (Which in the case of a coronavirus quarantine, what everyone’s worrying about now, is unlikely).
MREs are mostly for when you may have to travel light and want to be able to eat without cooking — or for if you worry that you may not be able to cook because, say, your house is knocked down by an earthquake. (Or if you think you might be too sick or shocked to cook, I guess). The chief virtue of freeze-dried food is that it keeps for many years, so once you’ve got it you’re covered for quite a while. Also you can get freeze-dried things that will augment whatever other food you have — fruit, vegetables, other things that don’t keep well in ordinary form. You might also want to stockpile things like canned bacon (it’s bacon!) and coffee and other stuff that might help augment whatever food you might be able to come by in bad times. Me, I keep a mix of stuff. I also keep some MREs, canned water, and other short-term essentials (blankets, clothing, medicine) in a shed outside that’s likely to be accessible in the event of an earthquake or similar disaster.
Also, if you’re stocking up, don’t forget about prescription meds — try to get a 90-day supply, which isn’t a bad idea anyway as supply chains from China, which affect a lot of drugs, may be interrupted — as well as nonprescription meds, toothpaste, toilet paper, paper towels, dish and laundry detergent, etc.
ANOTHER UPDATE: People in the comments are talking about water. Probably not an issue in a quarantine situation, but you might want a water filter, or LifeStraws, or a Water Bob. (Bumped).