You can add special character buttons on top of the search box.
When a user clicks on a button, it will insert the character into the search box.
In the WordPress Dashboard, go to “Appearance -> Widgets”. Drag the widget “Special Characters Widget” into the box “Search Bar Popups”. Click the downward pointing triangle to open up the Special Characters Widget. Now you can enter all your special characters separated by commas.
If you are self-hosting Webonary, you can download the plugin for the widget here:special-characters.zip