So I just got my voyager Generations springer this afternoon and when I gave him a go over everything was nice, save for the fact he had two left hands. I had ordered him online and I'm not sure yet if they'll take him back and I'm not entirely sure how this would count as far as requests go. But if it were possible for a helpful fix, could someone with customizing and kit-bashing know how, be able to mold a copy of Spinger's right hand?

I Also realize this may or may not be a big request but it's the only alternative I could think of aside from mailing him back and possibly getting something with worse QC issues.

Maybe it would be easier to find someone who got a Springer with 2 right hands and do a trade?

Before or after they promptly return it to the store they didn't buy it from online? unless you're implying you have one, but I'm not going to consider myself that lucky.

I don't have one. Actually I have not seen that in stores. That's a downfall for this area. But I just tossed that out there because I've seen other people looking for people with the opposite problem they have with their toys.

Do you know how to make a simple mold to duplicate parts, and possibly a good kind of plastic to use to make said parts?

Some guys here work on customs and even do stuff on Shapeways. Your question fits better for customizers and this section (The Workbench) is a good place to start:

http://forums.tformers.com/talk/index.php?showforum=97