A Bugbear (Long Limbed: reach +5 feet) wielding a reach weapon (10 feet of reach) can make a melee weapon attack with a reach of 15 feet.
If said Bugbear is a Battle Master with the Lunging maneuver, he can extend his reach of 5 feet for a single attack (achieving 20 feet of reach).
My question is: Can a player character's melee weapon reach be extended even further than that, or is 20 feet the absolute maximum?
Note that I'm searching for official non-playtest material; Unearthed Arcana would qualify as playtest material and be excluded. (Therefore currently excluding the "Giant Growth" Mystic Discipline from Unearthed Arcana).
If a spell/magic item/other can extend melee weapon reach (nonexistant example: "Scroll of Praying Mantis - Your arms grow bigger! You have more reach!"), it qualifies for the question. Material related to melee spell reach does not qualify.