Here is a simple 3D model for standing a shampoo, conditioner, detergent, or liquid soap bottle upside down. The diameter of the hole for the bottle cap is 31.5 mm. If you need a stand for a different diameter, let me know, and I’ll generate it, or you can download the Fusion 360 or STEP file and modify it yourself. I printed mine in white PETG with 15% infill.
I went for a simple semi-sphere shape, so that it would be easier to keep clean.
Here is what it looks like in use:
Download STL and CAD Files
This design is released under the Creative Commons Attribution NonCommercial license. Download the zip file with the STL, STEP, and Fusion 360 files below. If you find my designs useful, you can buy me a coffee.