http://www.amazon.com/s/ref=nb_ss_ba_0_9?url=search-alias%3Dbaby-products&field-keywords=foldable+potty+seat&sprefix=foldable+
We have this with a boy. No shield, but it does have an opening through which the organ in question can be pointed down, and my son was trained early by his father to "point it down."
It is flimsier than a nonfoldable seat, but it does keep the child from contacting the public seat at all because the wings come over the front of the seat. I also carry a supply of Lysol wipes in a ziploc to clean the seat off afterwards, and the whole package fits into a pouch about 6 x 8 inches.