The state park at St Augustine Beach is very nice. Reservations are a must.
February is prime time in Florida, finding anything is difficult. Sanlan in Lakeland usually has room. It’s a huge campground that counts on Canadian snowbirds. Given border restrictions they should have room. Stuff on the coast gets booked, often a year in advance. Tried to get a spot in Dunedin, a year in advance. They were booked!
Did find a site at a KOA in Clearwater/St Pete, it was $125 a night.. I’ve pretty much given up on winter camping in Florida and head west instead.