Here are some results :
Flash straight at cup :
Flashed bounced off ceiling/wall:
Using paper bouncer :
I happened to have some yellow paper in my scrap paper pile so I decided to have a try ( in fact I came up with the idea using yellow paper in less than 5 mins)
So there you are a new world of cheap filters as well as bouncers ( Ok not the most convincing filters/bouncers, but I can't imagine an easier to make and more practical if you suddenly realise you are missing a bouncer whilst on a shoot)
Enjoy and improve !
Yann