Here's a simple toothbrush holder I created when the free toothbrushes given to my kids by the dentist were too wide to fit our existing toothbrush holder.
It's relatively compact, small, prints with no supports, and provides a channel for water to drain out. If you print with ABS, you can vapor-smooth it so it's smooth and easy to clean.
The author marked this model as their own original creation. Imported from Thingiverse.