You will need to install a user script manager extension to install this script.
Adds the search to the top-left corner on every page on RARBG.
It's fixed there, meaning the icon is always visible even if you were to scroll down.
Click the icon to show the search. Click again or click anywhere else to hide it again.
On pages where there's normally no search the search is fetched from /torrents.php with AJAX.
If you get alerts of errors let me know.