Source for Orbit Ball

[artdutra04]

To anyone who has already broken one of these: can you find out what plastic material they are made of? I'm looking for an exact answer (such as acetal, PET, etc), not just something like "Its plastic, duh".

The reason I ask, is that after finding only four of them between two local Wal-Marts, the engineering and New England frugality instincts inside of me rang out. The orbit balls don't look very hard to [re]produce!

Using calipers, the interior plastic material is about 1" wide by about 0.1" thick (cannot tell for sure due to felt thickness), and the material they are coated with seems to be identical to the material used on stretchable Book Socks. The plastic (depending on the actual material) should be easily source-able through McMaster, and book socks aren't that difficult to find.

If someone can get me an [exact] answer within the next few days, I'll immediately place an order into McMaster to make about twenty or thirty of these balls, and then I'll raid the school supply sections of every store in the area like a loaded refrigerator.