Wood fence post? If so these are a pretty good deal and will fit.
https://www.amazon.com/Ubiquiti-Universal-Antenna-Mount-UB-AM/dp/B00HXT8TWC/ref=sr_1_4?crid=2LE6SHVI4BQHY&keywords=ub-am&qid=1644517160&sprefix=ub-am%2Caps%2C70&sr=8-4
Deal link: Amazon
^^Note: ^^The ^^deal ^^may ^^have ^^expired ^^by ^^the ^^time ^^you ^^see ^^this ^^post.