nobody has it working.
its really hard for a few reasons.
Generic problems with console guns...
the optic hardware for a TV and a VGA monitor. So you would only be able to get it working with TV - out.
you would have to write your own driver.
Did the nintendo guns even produce a flash? Some of them didn't care about location, but just if it sees red or white (when you click the button, it tells the game to flash red/white on whats 'acceptable'... These might be easier... but will only work with some games... you might also have to change the mame drivers to allow a simple white/red flag instead of the location of the screen (that people normally use with a mouse).
Next...
you COULD do it by buying a act labs gun... and hakcing it into a nintendo gun. would be MUCH easier if your looking for the nintendo look...