This insert will hold two Braun Oral-B toothbrush heads and two regular toothbrushes in an Ikea EKOLN 12011 https://www.ikea.com/us/en/catalog/products/10293045/ toothbrush holder.
The 'spacer' part will hold the insert up level with the top of the cup. Two pieces allows printing without supports.
This prints just perfectly on my Zortrax M200, you may need to tweak your printer or slicer to achieve the same results on your printer. It's also possible that these cups aren't made to Six Sigma quality standards and each one may be a little different.
I've included the Sketchup files for both parts in case you want to modify them. Enjoy!
Pictured are Ultrax in grey, Z-Glass, and HIPS in White, personal preference but I think white is going to be the final answer.