I needed a bookend that was able to be reinforced and made larger / stronger for large workbooks. Didn't find any that satisfied me so I created one in OpenSCAD, with the ability to customize various aspects of the bookend. Click the Customize button next to the Open in Bambu Studio button on MakerWorld to customize the various parameters which are split into groups (that you might need to expand to edit).

I recommend making the center piece a bit thicker, as it has started to bend for me.