Background 
I use a bunch of different action cameras for capturing mountain biking, motorcycle, and dirt bike riding footage, and I always try to use a tether to ensure that I don't lose a camera if a mount were to fail on me.  I've bought them in the past, but they're so simple it made sense to print them at home instead, and when I couldn't find an existing model, I whipped one up in Fusion360 and here it is.

Printing 
I printed it in PLA with a 0.2mm layer height using default settings including infill as it is so small it is practically solid anyway.  If you're worried about strength you could do 100% infill I suppose, but I honestly don't think it is necessary.  I used PLA to test but I would recommend using something like PETG as it is stronger and more UV friendly.

Due to shrinkage the 30mm base may be smaller than 30mm by a hair, and you may notice that when applying a 30mm sticky back.  If this is the case, adjust your print to 101-102% and it should be fine.

Additional Required Items
For this to work you'll need a sticky VHB or acrylic tape (like Alien tape), and something to act as the tether.  I already had a spool of 160lb test fishing line, so that's what I used for the tether, and for the backing I ordered these “Zonon Double Sided Adhesive Dots Clear Glue Point Tape Stickers Balloon Glue Round No Traces Strong Adhesive Sticker Waterproof Dot Sticker for Craft DIY Art Office Supply(200 Pieces,1.2 Inch/ 30 mm)” for $10 from amazon.

I do not recommend the commercial stainless tethers you can buy as they flop around in the wind and bang into the camera resulting in a lot of noise in your video.  The best bet is a high strength fishing line like I used.    

Assembly
Tie one end of the tether to the base using a bowline (see photo for example or use your own knot of choice that won't close on itself), and on the other end tie a bowline which you can slip into a secure area on the camera mount.  Then mount the sticky dot to the back of the tether and you're ready to stick it on your helmet/motorcycle tail/etc.

I hope others find this model as handy as I do.