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One alternative to deodorant rollers would be to create your own metal bearings (which would be hard). We learned that the deodorant balls didn't really roll against the plastic, they just decreased the friction between the internal mechanism and the plastic sphere.
I'm not sure, our lab technician used a router to position the sphere, then used a small drill bit to create the dowel holes.
We ordered 2 custom hemispheres with NO lip. Together, they created a 24" sphere, which are the life-size dimensions of BB-8. If you want to go a little smaller, you can get 2 hemispheres that create a 20" sphere for only $100.
Our lab technician helped us drill 36 dowel holes equally spaced on each of the plastic hemispheres, then we used really small dowel rods to attach the hemispheres...a lengthy process, and in the end it didn't even keep the sphere together. We ended up just duct-taping around the seam where the hemispheres connect.