I don't know if Mike has made an announcement here or not, but he has a prototype Super Punch-Out joystick, which, in kit form, can convert an original standard Nintendo joystick, or one of his reproductions, to an SPO joystick without making any permanent changes (no drilling or anything). He came up with a very clever way of attaching the bracket for the 5th microswitch. Instead of screwing directly to the side of the base like the originals do, he designed the bracket to be secured by the same carriage bolts that secure the joystick to the control panel, which is how he made it so people wouldn't have to drill their joystick or make any other permanent changes to convert it to an SPO joystick. So if you want an authentic way to control SPO or Arm Wresting in MAME (2-way restrictor should be used for Arm Wrestling rather than the 4-way for SPO), this is it; and of course this is also perfect for converting an original Punch-Out to SPO or AW.
I never thought I'd see the day. Original SPO joysticks are about as common as hen's teeth, and their lack of availability was a major stumbling block for people wanting to play SPO correctly.
I am in no way affiliated with Mike's Arcade BTW, it is just that I've been hoping for a reproduction of the various Nintendo joysticks, particularly the rare SPO joystick for such a long time.

You can see in that picture the clever no-modification method of attaching the bracket for the 5th microswitch that Mike came up with. More pictures
here.