a) Are you sure it's ProDOS, not DOS3.3? Older macs with SuperDrives (the 3.5" kind, not the DVD kind) could read ProDOS, but not 5.25" disks of course.
b) I think you'd have a heck of a time finding any Mac with a 5.25" drive. You could transfer to 3.5" with an Apple II and then use an older mac to read the 3.5" disk, I suppose.
c) You could connect an Apple II via serial cable to a Mac and use ProTERM or some telecom software to send files back and forth (not for the faint of heart).
-Rob