Underwear, padded butt

OK, I'm working on an outfit for Halloween. It is a cartoon superhero. Wearing tights and think it would be better to try a under brief with a padded butt. Has anyone bought a pair before? Any brand better than another. Did it look realistic? Stores available. Thanks for the help.

Which one? Do you have a flat butt?

While I haven't purchased any myself, I know that undergear sell them. I've bought the padded crotch undies from them and found them very satisfying. Hope this helps!

I just have a normal build, but superheros, done as a cartoon, need to have a hightened look.