Yes the hot fix flex PCB can be applied to version 4.2 of the Miniscope. Unfortunately I don't know of any group directly selling an assembled hot fix PCB. You likely can contact OEPS or LabMaker and ask it they will sell you some (feel free to CC me on the email and I can help try to push this through).
You can also pretty easily get everything for this hot fix yourself very cheaply. Order the flex PC from OSHPark and the components from Digikey.