It defnitly sounds like you want to wear a plug, so go ahead if you feel like thats a good idea, or wait for the next trip there
Bodywriting? How about something like 'Must always wear Diapers', 'Keep in diapers 24/7' or 'be careful, might leak'.
Somewhere on your butt-cheek would be cute, although might be hard to write there if you need to do it on your own.
I think you are up for a fun time
I visited Amsterdam a couple of times, but i never really went to the redlight district.