I am surprised that Grove level shifters are not part of the M5Stack hardware offering.
Just today I went onto JLCPCB and designed myself a PCB that can fit in shrink tube and has a Grove socket on each side, the board has a level shifter that converts a Grove (5V power + 3.3V logic) to pure 5V power + 5V logic. (it's a level shifter board that generates its own 3.3V reference with an LDO). I made an order of 90 boards at a shipped cost of $135, so a little over a buck a board. I am just surprised nobody seems to sell this, least of all M5Stack with a core offering of 5V power + 3.3V logic on just about everything.
By the same process I could quickly make a set of boards that takes 5V power 3.3V logic from one side, and gives 3.3V power 3.3V logic on the other (just by duplicating the design, rearranging the components and deleting the level shifter). I'll probably do it the day I need it. Or maybe sooner.