My textbook has a lot of pictures like this one of unusually shaped objects:
I found a scrap piece of 3/4" plywood and used a bandsaw to cut it into an "odd shape." Then I drilled three 1/2" holes through it, one on each end and one roughly at the center of mass. I cut three 8" pieces of 1/2" dowel, one for each hole. The dowel was snug enough that when you rotate it, the whole piece rotates.
The wood is hefty enough that you really feel a difference from the center axis to one on the end. You can feel a slight difference between the two ends but not as much as I'd like. I may carve out a bit more so that the difference is easier to feel. Below is a video of me spinning it to give you a sense of it.