Fans are either 25 or 30mm square - dimensions to the outside. I would measure and verify but here are some 30mm selections as I am pretty sure its a 30mm on that esc (1-3/16" roughly).

This one has the right connector already on it.
https://www.amazon.com/Gdstime-30x30...m+fan+5v&psc=1


Amain fans mostly have servo jst style connectors for running motor fans. You can always switch out connectors but can a be a pain.
https://www.amainhobbies.com/ruddog-...p-0093/p538051