Some nouns don’t have a plural form, “species,” for example. Here’s what can happen if you make up a plural:
As Searses and Toys-R-Uses evaporate from suburban shopping centers, thrift stores are shuttering, too.
Change them to adjectives and you get rid of the awkwardness: Write “Sears and Toys-R-Us stores…”
That latter is a good example of the rule (usually applied to acronyms) that you should add an apostrophe when you make a plural whenever not using the apostrophe could cause confusion.