Children's Water Cup Holder for Bedroom

My kids use spoutless training cups (e.g., Munchkin Miracle 360 Trainer Cup) for drinking water during the night. However, if something pushes on the silicone membrane, water will leak. Because laying in a puddle of water all night is no fun, I designed this cup holder that can be attached to a vertical bed post with zip ties. 

The cup holder is tapered from 77 mm at the top opening, and 50 mm at the bottom. 

Happy printing :-)