Waistband Clip

This is a copy of Skinny Clip Waistband (designed and patented, and not by me, info is at https://www.skinnyclip.com/about.html). I wanted to try before I buy, and so roughed it out and printed a few at different sizes. It does work well to keep loose pants from falling down. I like it especially for jogging shorts or sweats that have lost their pull string. Better than a belt.
The "Big" version is probably close to the standard size. The other version is for thinner or lighter clothing.
To use, you straddle the two longer legs over the waistband of your pants (while wearing), and then twist either 90 or 270 degrees (depending on how much tighter you want your pants), then you clip the shorter leg over the waistband to hold it all. If you like this and it works for you, please consider buying the real product from the real inventor.

For printing, you will likely want to flip the models 90 degrees so they are lying down flat.