What is the correct spelling of "buyer* remorse"?

Apostrophical query:

• a) Buyers Remorse
• b) Buyer Remorse
• c) Buyer's Remorse
• d) Buyers' Remorse

My guess is b or c, as it seems like any example is talking about the remorse of one specific buyer, but since it is a collective term that happens universally, perhaps the possessive plural is accurate. I suppose there’s potential that it’s a context-sensitive decision, deciding whether you are talking about exactly one buyer or about buyers in general.

Yes, it does happen to everyone, but the remorse belongs to each person individually. "Buyer's remorse" is the remorse experienced by a buyer. So the answer is (c).

Wikipedia agrees. Similarly the Corpus of Contemporary American English gives 36 examples of "buyer's remorse", but "buyer remorse" has just 1, and there are no results for either "buyers' remorse" or "buyers remorse".