I use a handlebar mount for mine, this one specifically: Fouriers Out Fromt Cycling Watch Mount For Garmin Forerunner Fenix Alloy https://www.amazon.com/dp/B074QQQ2XH/ref=cm_sw_r_cp_api_glt_fabc_BS7YZ71JS7ZNB4JAKT63
There is a cheap rubber one that basically just simulates a wrist that goes around your handlebar top for about $10.
I had originally planned to do triathlon/duathlon when I bought my watch but after multiple stress fractures a physiotherapist said I should avoid high impact exercises like running.