First one I found on amazon. There might be cheaper options. I searched for "Garmin 22mm arm band."

https://www.amazon.com/Euler-Elastic-Armband-Companion-Instinct/dp/B09X3HTLFN/ref=sr_1_1?crid=29N5AIAZYNW0H&keywords=garmin+22mm+armband&qid=1665487048&qu=eyJxc2MiOiIwLjAwIiwicXNhIjoiMC4wMCIsInFzcCI6IjAuMDAifQ%3D%3D&sprefix=22mm+armband%2Caps%2C123&sr=8-1