The Gotek floppy emulators are really popular in the retro scene. I have one modified (firmware update) to work with my Amiga 500.
Can one be made to work with any of the classic line of Macintosh computers?
The Gotek floppy emulator appears to only support two firmwares: Cortex (Amiga only) and HcX (Amiga, Atari, Amstrad, and Spectrum).
There is another floppy emulator, the BMOW Floppy Emu, which supports classic Macintosh hardware (Macintosh, Apple II, and Lisa Floppy/Hard Disk). There are firmware downloads on the linked page.