I had the same issue and came up with a straightforward and inexpensive solution.
And you can have confidence in it, because I'm a smart ass.
Don't use plastic. Weather and UV rays will break it down if the squirrels and coons don't chew it up first just for fun.
Buy this in the 12" diameter:
View attachment 4778
Cut it in half. Trim as needed for the acreage you want blocked.
(Because it's already rounded, it will curve nicely around a round cage; modify for a square cage).
Drill a bunch of holes about 4" apart around the edge of the sheet; they should be large enough to accommodate a sturdy zip tie. You probably won't need to use all of them, but they'll be available if you need them.
Spray paint both sides dull black. (This will reduce glare from the light source from rifle or camera).
Tag to feeder cage with only a couple of zip ties and test for placement.
Secure with lots of zip ties.
Expect more noise as the corn hits the metal, not necessarily a bad thing if you want the beasts to know when it goes off.
The corn most likely will not actually be deflected in another direction; it will simply drop straight down.
Again, not necessarily a bad thing.
Mine has been up for over four years through all kinds of weather and still does the job.