Get a wide angle adapter for a smaller sized lens (I used a .5 58mm lens thread) and cut a hole and mount it in black cardstock. Hold 2-3" from the lens and it should work great.
Short, short clip of it here, about 10 seconds in just after the tractor. Shot with Zeiss 10-1 72mm front thread on 16mm.
an easy way to achieve the peephole look is to just take a roll of black gaff tape, tape the inside of the roll so that the cardboard tube that the roll comes on isn't showing then hold it up against your fisheye lens or wide angle lens.
I have used this trick on a couple of features that i've worked on. Works great and is fast and painless.