A colleague of mine has this Garmin VivoActive HR smartwatch and the little ring to prevent the wristband from flapping around had broken, so I modelled and printed a replacement for him. I didn't even bother looking whether there were already existing models (which would have been a pain anyway, given how unusable Thingiverse is these days). Now that I have checked, I found at least 6 different existing ones… apparently this wristband is pretty poorly designed. I am pretty sure the replacement printed in rigid.ink ‘flexible PLA’ will last much longer. If not, it takes only a few minutes to print a new one.
Because extreme overhangs and supports are usually a no-no when using flexible filament, this design puts the little tab on the print bed. Functionality-wise this makes practically no difference but it makes for an easy and clean print.
To get the ring onto the strap, you will probably need to remove the clasp unless you have used a sufficiently stretchy filament.
Rigid.ink Flexible PLA