Thanks- I ran across a cool tutorial on how to do this. (My fake lens hood was way less professional looking than theirs- pretty much just held it in front of the camera.)
I gave this a shot using my wife's Cricut paper cutter...
...but I wanted to see if I could improve the bokeh shape near the edges, so I cut out a 1 1/4" circle with a 1/2" Mickey head in the middle, and carefully taped it to the edges of my 50/1.4's inner element. (I tried on Sigma 30/1.4 first but it doesn't have a lip around the inner element to tape to)