I think some of the people replying didn't realize this was a question on the Class B section of the forum. Or maybe have never seen the inside of a B - space is extremely tight. I've never seen a bathtub in a Class B where you could stow trash.:)
Our LTV Free Spirit had a coated wire grocery bag-frame screwed onto the inside of the below-sink cabinet door. It was handy and did not interfere with the contents stowed under there. Of course, it only held as much as a grocery sack holds so we took out the trash every day.