I've seen so many spearguns; it's ridiculous. I am sure several other of us are in the same boat. I agree 100% that the holster is most likely a Nemrod. In fact, I have seen a Nemrod holster (new) that is almost identical. I am also with Chris that is speargun may not be a Nemrod. I have seen mannnnnnny pics of Nemrod spearguns, and while many are close, none of them have had the rectangular butt-grip. If it is a Nemrod (which is what the Bespin blaster was), then it is the most obscure non-exsistant Nemrod they made.
Btw- What are the chances the original thing was brown? She sure looks very shiney and very stock to me....