There are numerous picture of HMS Amethyst on the net from various sources and easily obtainable.
I am sure you have done your research so forgive me if I am teaching Granny here but the actual HMS Amethyst was used in the making of the film The Yangtze incident which tells the story of that fateful mission when she was set upon in 1949 in China.
During the film the special effect film makers accidentally blew a hole in her side and flooded the engine room.She was then unserviceable and took no further part in the film.
HMS Magpie took over the part of Amethyst (HMS Magpie was commanded by HRH Prince Phillip (but not at the time of the making of the film)
HMS Magpie was a sister ship of the same class and modifications as Amethyst to the best of my knowledge.
The film Yangtze incident is readily available to buy on EBay and other sources and if purchased would give you a real set of pictures to work from if you were able to stop and freeze the film as needed.
I won’t bore you with the technical facts of the ship as I am sure you have already researched her history.
Hope this helps.