We are on 4.26.2 but need to install 4.26.1. 4.24.1 doesn't show as an option for install. Is it available?

The Epic Games Launcher, I believe, displays a limited set of versions. I didn’t read the link provided above by @UphillGames. But if that doesn’t work you should be able to pull the source from GitHub, checkout the tag you would like, and build it.