these also work
https://www.amazon.co.uk/EventClip-BibClips-running-cycling-numbers/dp/B00GY6A9J6/ref=sr_1_9?crid=2XRKZ1OSLFX6W&keywords=race+number+clips&qid=1644237871&sprefix=race+number+clips%2Caps%2C56&sr=8-9
I had been looking at those, it seems easier than a belt if they work.
@HatBeard started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
these also work
https://www.amazon.co.uk/EventClip-BibClips-running-cycling-numbers/dp/B00GY6A9J6/ref=sr_1_9?crid=2XRKZ1OSLFX6W&keywords=race+number+clips&qid=1644237871&sprefix=race+number+clips%2Caps%2C56&sr=8-9