I was quite late on the uptake, but in 2008 Buichi Terasawa/AGR released 4 official Psycho-gun replicas to commemorate the 30th anniversary of the series. There were black and blue, cheaper and premium variants available retailing about 2000 yen and 9000 yen respectively.
I managed to find the cheap ones easily, but the premiums were nearly-impossible to find 3 years later. My savior ended up being Hobby Link Japan. Though it came at a hefty $160 after shipping, this hole in my wallet was well-worth it because this Psycho-gun looks and fits much better than the cheaper counterpart.
On the last note, a good friend of mine (Nico Robin from One Piece) surprised me beyond belief with a Cobra figure for my belated birthday.