Plaground3d's Flex Dragon design is well done, easy to print from any material, looks neat, flexes just as expected, and seems robust.
Two modified versions,
If you choose to download this version, please consider downloading the original also.
The file with the interior magnet slot is a .3mf file. I have tested the file successfully on Prusa Slicer and Bambu slicer.
I used these magnets from Amazon. To print these, I used PLA, 0.2mm layer height, 15% infill.
The author remixed this model.
Added slots for 6mm diam magnets.