This is my 3D printable Nalgene strap. PETG is flexible enough for the large ring to slip around the bottle's flange. The cap side is a snap fit. Since my original strap broke, I have been printing these about every month (they do wear out in PETG). In the future, I would like to try printing it in nylon, I bet it would last longer.

any nozzle 100% infill