I took a look at www.dictonary.com, and the word "rare". Besides the ever popular "uncooked", it did offer several definitions that could be used to support my use of the word 'rare" to describe generally unavailable chips. However, down near the bottom of the page, I found this:

Syn: Scarce; infrequent; unusual; uncommon; singular; extraordinary; incomparable.

Usage: Rare, Scarce. We call a thing rare when but few examples, specimens, or instances of it are ever to be met with; as, a rare plant. We speak of a thing as scarce, which, though usually abundant, is for the time being to be had only in diminished quantities; as, a bad harvest makes corn scarce.

So, I will no longer use the word "rare" when I mean "scarce", and vice versa. But I reserve the right to contact www.dictionary.com and ask that the definition I quote be removed, because it makes me look bad.