Knog Plug Backlight Strap

Print with flexible filament like TPU. I tested the version for the 27.2mm seat posts, the 31.6mm version is just an educated guess. But the design is parametric:

https://cad.onshape.com/documents/4f67063328ba5b9ca9d0aec0/w/41f608343b6b1f985d89ec07/e/3c32e8dcdec584bf55b772ed?renderMode=0&uiState=66a3b4a37c8cbf300ee5ba19