I feel your pain!!!!!
A co-worker mentioned that he has an original Pac-man cabinet that isn't in too terrible condition, but the monitor is definitely fried. it apparently works otherwise... but a new moniter is going tobe a few bucks.... for the same price i could probably cobble together a Mame system that would run Pac-man and a computer 19" monitor to put in it... but then it isn't original anymore.
I don't actually like Pacman THAT much, so i thought about putting a 60in1 board into it, but then again, i don't want to put any holes into the cab because it is apparently all original. and to top it off, the missus would not be too happy with having 3 cabs in the house.....
I say to restore Defender however you can.... if it's all gone, and the side art isn't too terrible, put a defender-mame in it while you source parts.... Doesn't Happ have a 2-way stick? If you are a defender fan, i say go for it...
Me, my youth lies with "Exciting hour" (though i've yet to see an original cab EVER!)