A drag chain needs to be easy to print, openable and configurable and should pop together with no metal pins. I couldn't find one that ticked all these boxes so I spent far too long designing my own.
There are only three parts here, the body, the cap and a universal mounting/end piece. No pins are required.
Print this in PETG or ABS as PLA seems too brittle for unsupported chains.
The design is parametric and the Fusion360 files are included so that you can change the width or height as you need. Make these changes in the "Parameters" table only or you'll break the model.