Thanks for including Search by Image! Here are some more legacy add-ons which could be mapped to it:
https://addons.mozilla.org/en-US/firefox/addon/google-search-by-image/
https://addons.mozilla.org/en-US/firefox/addon/search-image-by-image/
https://addons.mozilla.org/en-US/firefox/addon/who-stole-my-pictures/
https://addons.mozilla.org/en-US/firefox/addon/search-image-everywhere/