I believe any interface that uses the later specification (IBM PS/2) disk controller can talk to the ED or 4MB floppy drives - they are 4Mb unformatted, but only with their specific media for that. You can find some good info on these drives and the controllers here:
https://www.retrotechnology.com/herbs_stuff/drive.html
There is, I believe an extra signal on the floppy cable for density selection - so the new interface gives 2 density selections - 720 / 1.44M and 2.88M (on a PC) QL can format these to a higher capacity - hence 780, 1.6 and 3.2 capabilities - although I think Gold and super gold card limited the middle density to 1.44 for compatibility with PC disks.
You may find some cheaper 2.88Mb floppy drives from ex IBM equipment - but they are sometimes odd physical sizes (taller) or lack a button on the front and support electronic eject, I don't know that the later disk interfaces for the QL do support that.
I recall that Mitsubishi/Panasonic (Matsushita), TEAC, Sony, IBM and Citizen all had drives at 4MB back in the day.