Browsing the eclipse marketplace, the current instructions for Teams Explorer Everywhere is to download the plugin from its GitHub repository and then install it in Eclipse from where its zip/archive file is saved on disk:
GitHub Page for Team Explorer Everywhere:
https://github.com/microsoft/team-explorer-everywhere/releases
Additional instructions for installation:
https://stackoverflow.com/questions/5482554/how-to-install-plugin-for-eclipse-from-zip