I hav e to agree with STG. If you use a weapon from another serial, fans are going to recognize it right off. Almost as bad as a painted, unmodded Nerf rifle.
We have some guys making some really cool custom and canon Star Wars weapons over at Mercs in our Trading Station. Some are casted items that you'd have to buy from the prop maker to get... such as the DE-10, the JE-38 handblaster etc.
However, we also have a guy making what he calls EE-2's and EE-1's. The EE-1 is basically an EE-3 without the stock and scope and the EE-2 is a handgun style based on the EE-3. He sells them for about 40.00 each however, they are easily made using a Hasbro Darth Vader or Anakin Skywalker lightsaber and an old Play Station revolver style video game gun. I purchased an EE-2 from him and just completed making my own. My own I used one of my kids broken lightsabers, purchased the revolver on ebay for about 10.00 shipped and used 1 tube of 2 part plumbing epoxy putty. Overall it cost me about 15.00 to do it myself.