I ordered a replacement screen from the M5Stack store on Aliexpress.
New TFT display + bezel arrived 15 days later.

Installation was reasonably straight forward.

You'll need:

Soldering iron - I'm using old faithful Jaycar Duratech TS-1554 20W/130W Solder - I'm using cheap 0.5mm Sn 63 / Pb 37 / Flux 1.2 Flux - I use a pen T6 Torx screwdriver - I have one of these sets

Steps:

Remove bottom battery/breakout board 2x T6 Torx screws hold the PCB in place Slide speaker out (careful of it's thin wires - I broke mine) Slide PCB sideways and lift slightly. The display ribbon cable prevents it from being fully removed Push the display + bezel from behind to detach it from the case Remove the bezel from the broken TFT Rotate the PCB 45 degrees and remove from plastic shell, to avoid damaging it Flip TFT 90 degrees revealing its flexible cable Detach the TFT by applying a little flux + solder and gently prying while heating the pins with a soldering iron Apply flux to the solder pads and stroke each with a soldering iron to create a smooth finish. There should already be enough solder remaining, if not, add a tiny bit more and stroke smooth Place the new TFT over the pins and precisely hold in place with your thumb while applying power to check the display works Solder pin 1, check alignment and adjust if need be Solder the remaining pins. Get some bright light and a magnifying glass and make sure none of the pins are bridged. Or use continuity mode on your multimeter to check adjacent pins Insert the PCB + new TFT back into the plastic case, slide PCB sideways and attach Torx screws. I accidentally detached one of the speaker wires earlier, so with the new TFT flipped out of the way, resoldered the speaker wire. In doing so, I detached the other speaker wire! So I swapped both for new thinker wire, salvaged from a Dupont ribbon cable. The wire can't be too think as it needs to sit between the TFT and PCB. Reseat the speaker Sit the TFT in place and remove the protective cover (green tab) being careful not to touch it with your oily fingers Remove the sticker from the back of the bezel and insert the 3 plastic buttons Attach the bezel onto the plastic case and press firmly Plug in USB and boot Press 3 push buttons to cycle through RGB colours It works!