Do you have a whole bunch of Nato watch straps lying around in a messy bunch?
Well, here is your solution.
There are three files included - one for a 22mm band, one for a 20mm band, and one for a 18mm band. I recommend printing the part with a raft to ensure good adhesion to the bed.
The Nato bands in the picture (and the ones this part was designed for) are from NatoStrapCo.com