Hey,
there's not a lot more I can say about where I got em from. I've been running a small Bionicle-centered BL store for a while, which is why I'm looking through lots to buy multiple times a day. The prototypes/misprints are from such a lot. It wasn't a cheap lot either and I was about 80% certain that those parts must've been bootlegs/fakes, but I was just curious enough to take the gamble. The rest of the lot was nothing too noteworthy; a few Toa Mata, a few Turaga and the Nui-Jaga, along with a few loose parts and two decks of the Bionicle TCG.
I guess the best information I can provide is that the lot came from a city in the very north of Germany, very close to the Danish border, so it's not unlikely whoever sold them knew someone at Lego back in the day.
I'll try my best to get images with other parts of the same color the next time I get the chance, since I don't currently have the sapce or access to a nice photo setup. But I can guarantee that the material is the exact same as Lego's ABS plastic.
-Owls