Can anyone recommend a good PPFD / DLI / PAR meter?

I’ve been trying out a couple free apps for iPhone that got great reviews for being accurate. The Photone app requires some purchasing to unlock the full benefits. The PPFD Meter app seems to work fairly well, but I’m getting some inconsistent readings from time to time.

Trying to set up two different lights efficiently and it’s proving to be harder than I thought. Is buying an actual light meter the way to go? I’m pretty sure I’m using the app correctly. Have the profile selected for the type of light I’m using. Should I put a piece of paper over the camera lens to more accurately measure coverage and intensity?