Actually it sounds more like it would be a type of plastic pants in an AB/DL version of the Sims. I can see it now The Sims 3(The Fetish Edition) Infantilist Expansion.
They're a lot thicker then normal plastic pants, and the extra-wide leg bands really help with pinching and chafing. You still have to take care washing them, though, or they start to get stiff.