USS Phoenix was a Brooklyn class Cruiser laid down in 1935 and transferred to Argentina in 1951. Although I have found some reference to Brooklyn class in 1:350 in resin and metal, they are between $250 - $350, a tad pricy for this GB me thinks. One other I have found is at Netmerchants but currently out of stock and that is the USS St Louis (CL49) which is described as a Brooklyn Class 1941 so about the same period as the Belgrano/Phoenix. Link here. I suggest that you search for Brooklyn class and try to get one that is similar to the one you want. I know classes did vary slightly but I assume that at this scale, unless major changes were made, one of the Phoenix's sister ships would be close in appearance.
Wikipedia lists 7 Brooklyn class ships, one being the Phoenix but the last is CL48 so I am not too sure about the St Louis which is CL49.
Sorry I could not be of more help Scott.