You can buy "overmolded" weapons from ToyWiz (the Plasma Pistol and Needler) as exclusives. But as for them being available as mass production items, I say no. Overmolding (so I hear) takes a lot of time.
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Flickr! Last updated: October 19th, 2009. No big MOCs from me for a while, I've got a vignette I'm working on, and it's using my best pieces.