OK, so watches come with a few different standards for the pin length, the gap between the two metal rings that watch pins pop in to. The pine time seems to use 20mm bands, so searching for those on your internet purchase place of choice is the next step.
https://pine64.org/documentation/PineTime/Accessory/Watch_band/
The documentation links to a couple of options in the link above, but any of the bands for a galaxy watch which are 20mm will do just as well. All you need is to make sure the pins are for a 20mm watch and the rest works itself out. Good luck!