I have read about people using MP soap and putting them into tubes like large lip balm tubes or deoderant type tube.  You don't need a soap dish.  Just use and put the cap back on when you're done, no mess of a liquid soap and you can fly with it no problem.  Good for camping and situations when you need soap and there isn't any, or you just want your own soap.  I think it would work better not as a bathing soap, but as an emergency hand soap.  Only yesterday I was at a restaurant and their bathroom was out of soap.  Hmmmm… what a great time for a small travel soap in a tube.  I just received an order of solid lotion tubes and small deoderant tubes.  I think I might try this.