This print-in-place locking bag clip has been designed so that it can be printed without supports, has a fun curvy shape, uses an outward angled handle for easier one-handed use, and is a nice size at just under 6 cm when closed.
I'd recommend you set the “Vertical Shells → Perimeters” option to at least 5 for increased strength. In addition to the STL, I'm also attaching the gcode and 3MF file I used to print the ones shown in the pictures, as well as the Fusion360 file if you'd like to make adjustments.
Update (2023-07-03): The original “Cam Lock Bag Clip.stl” (which I'd still recommend you start with if you're printing in PLA) is designed with a .2 mm tolerance around the pivot joints. If you have trouble with the plastic fusing in your print conditions though or are printing in other materials - such as PETG, I've now also attached two versions that increase the spacing tolerance slightly (.3 mm and .4 mm) which you could use as an alternative.
This is a complete from-scratch design, but there are many great cam locking clips here on printables. Although notably different, I've marked this model as a remix of the very cool model that ‘jfedor’ did which used a similar approach for making a clip printable without requiring supports (which itself was a remix of Andrei's popular version that does require supports).
