You know what, you are correct. I hadn't noticed till you asked, but those lights don't have the locking nut behind them to hold them in place. That's my mistake. What you would need is something like these, which have a threaded back, so you would be able to tighten it against the back side of the bumper.
https://www.amazon.com/gp/product/B07CMN6FD5/ref=ox_sc_saved_title_7?smid=AQU08BEB4MN2K&psc=1
These look a little bit larger
https://www.amazon.com/dp/B07CWQZ212/ref=sspa_dk_detail_3?psc=1&pd_rd_i=B07CWQZ212&pd_rd_w=lelbM&pf_rd_p=45a72588-80f7-4414-9851-786f6c16d42b&pd_rd_wg=9TmC9&pf_rd_r=TEFM1K3KC8J7P5GCRASP&pd_rd_r=21117b32-a1e3-456a-95e8-2e60bbb7809f&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEySkRMTEwyUkMxTThMJmVuY3J5cHRlZElkPUEwMDQ4MzAyMTMwSExJQTQ3Vlg2RiZlbmNyeXB0ZWRBZElkPUEwMjk3MDg5MjZQNk5DWktDSllMTyZ3aWRnZXROYW1lPXNwX2RldGFpbCZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=