Is there a noun that doesn't have a plural in any of its forms?

While attempting to answer this question @ProgramFox has been trying to come up with an example of a noun with no plural.

The best I've come up with is egotism and Judaism. (Fluxmay be a viable contender as there is a related question asking about its plural!)

Some of the contenders I've already shot down are air, water, and money. (Airs, waters, and monies are all legitimate plurals.)

My question is, a) Do my two examples have actual plurals? b) Are there any other non-ism nouns that don't have a plural?

There is a term called "singulare tantum":

The term for a noun which appears only in the singular form is singulare tantum (plural: singularia tantum); for example, the English words "information", "dust", and "wealth".

Singulare tantum is defined by the Shorter Oxford English Dictionary as: "Gram. A word having only a singular form; esp. a non-count noun."

There is still a plural form of "information" but I think it only applies to law.

Most senses of the word “information” are uncountable. The legal sense, referring to court filings, is one that does form a plural.