Medical coat, trousers, hat, stethoscope(sp?), large white painted box on chest, two holes cut in it, lettering on front to say "Mobile Breast Screening Unit". You will be pleasantly surprised how many drunk women will try it for a laugh.
I took the cowards way out recently for an 80's party. Big white T shirt with CHOOSE LIFE on it (you can buy them online) , pair of jeans. Job done. Mrs had 'FRANKIE SAY RELAX' shirt on.