About how much will it cost to fix a small EVAP leak on my car?

I scanned my car with a CAN OBD2 and the code came back PO456. It says that means there's a "EVAP Emission Control System Leak Very Small" I don't think I can fix this myself. Does anyone know a ballpark estimate of what it might be if I take it to a mechanic? Thank you.

Added (1). I have a 2007 Ford Escape XLT if that matters at all.

This tends to be a bad gas cap, the locking style are notorious for leaking also, so get a new non-locking one and reset the code by handheld unit or pull the neg on battery for 5mins and put it back on to reset the fault code.