I have tested all the spare Amiga external floppy drive interfaces I have and they are all working!
The one I have which would best fit your PC880B enclosure has only a single ON/OFF switch as well as the 23-way D-type connector on the back, so you may have to enlarge the cut-out on the back panel to accommodate that, but it should fit without problem otherwise.
Attached is a scan of it fitted to a Motorola MPF-920E drive. It is complete. Let me know if you would like it.