With a HOB filter, you could make an in tank overflow. Get a plastic cup and (magnet, glue, clamp, whatever) it just below the surface of the water. Stick the input pipe of the filter in the cup and have the filter return back into the main tank as usual. You'll probably have to play with the cup level a little to find a nice equilibrium, but it can be done.

While this won't let the filter skim the surface, it will at least concentrate the film and gunk out of sight. The cup is just a suggestion, you could use some plexiglass panels and make a nicer looking box.

Good luck.