You can check Daz for some figures. They're based a bit more on the movie adaptations, but I know I've seen a few there.

Start here: http://www.daz3d.com/creatures/aliens

As far as the princess goes... try http://www.daz3d.com/zavia-red-martian-princess-for-v4 and http://www.daz3d.com/martian-princess-base which follow the book a bit more for her. 

hope that helps. :-)

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