1 box of prunes
Eat, stay near a toilet.
If it's the kinky, fetish, self-indulgent, pampering you're after, have your girlfriend/wife pin a diaper on you.
If you're willing to be honest and admit you just want to stick things up your ass, you can do that by yourself too. Barbie's head works wonders, as does the bendy head of a rubber toothbrush.