I have used the Audio Technica 100 series. I use their tap that goes on a EV hand held and makes it wireless. This is a basic system and still cost me $800 +
What I don’t understand you say its not for ESPN so it doesn’t have to be outstanding quality, why ? you have a great camera, audio is half of your picture , why not strive to get the best audio ? Look into renting some gear. Or maybe find a begging audio person that is just starting out and maybe give you some help and team up with you.
Good luck in your project
Later
Tom