I have long held the view that it is well to be cautious and to keep a low profile when purchasing certain perfectly legal supplies.

AFAIK it is perfectly legal to buy large qauntities of MREs tinned foods, batteries, water purification tablets etc.
I would however prefer to keep a low profile in such matters.
Apart from the risk that the government might think that I am a terrorist, Is it wise to be known as a "hoarder" in the event that TSHTF in the near term.

If there should be sudden release of toxic gas, do you really want to be known as the person with 10 gas masks ? Suppose that the release WAS by terrorists, people might conclude that you were involved and therefore took measures to protect yourself.

If some disaster resulted in large scale food shortages, do you really want to be on a database as having purchased loads of MREs ? no matter how lawful that purchase was.

There are many ways in which stocks may be purchased without attracting attention.
Pay cash, never charge or credit.
Visit different stores, where you are not known.
For mail order, have deliveries made to your work address.
Consider use of a prepaid payment card not linked to your bank account.
Ebay is pleasingly anonyomous, anyone can register under an assumed name and pay via paypal and a prepaid card, deliveries NOT to your home.
Dont attract attention in local stores, but always buy a little extra.To buy 36 tins of tuna might be commented on or remembered, no one will take the slightest notice of you buying 2 tins a week.
It would be a bit odd to buy 24 blankets and 48 sheets at once from a retail store and might be remembered. So dont ! go to a wholesale outlet, pay cash and ask for a receipt made out the "beach view hotel" or some such.

There are many activities that are perfectly legal, but still better not advertised.