Check out Long Mountain Outfitters website. He has a list of the weapons from Ellis he sold and the MP5K's and Mariners are on the list. Also if you look at the photos from Ellis Armory you can just see them above the two hard chromed AC556's from Escape from LA. They are on the right near the door when you are looking at the wall with the Thompsons, Bars and Stens.
Here's a link
http://www.longmountain.com/movieguns/ellisgunlist