Three tools are used at various Wikisources, which don't have very beautiful icons in the indicator area:

• https://book2scroll.toolforge.org/index.html: usually uses
  
• https://bookreader.toolforge.org (used at bnWS): uses
  
• https://checker.toolforge.org
  

These should have a unified theme with the rest of the site (i.e. similar to https://commons.wikimedia.org/wiki/OOUI_icons)