Somewhere on FR there was a topic (circa 2005? 2006?) regarding some armor that were apparently from Actium; I remember it, but a search a few years ago didn’t turn it up. A bronze ram I believe has been found on the sea floor.
Likeliest place to find bronze rams would be on a wreck carrying salvage — they recycled metals just as we do today. As you said, a bronze ram would be reused if possible.
According to the late Lionel Casson, there was an arms race of sorts during Classical Greek / Hellenistic times, with larger and larger warships, to the point that the pinnacle development was too large ever to be used. The Romans conquered Greece, liked the ship (still tied to the dock where it entered service), and towed it to Rome, where it became a tourist attraction.
The upshot is, when warships with rams got replaced, they were replaced by a larger version, and the bronze rams would have been newly built to fit, psssibly reusing previous rams by melting them down (not sure that works with classical bronze).
With so many warships lost in combat there must be quite an amount of metal remnants remaining, especially rams, but you never hear of any active search for such. I think about six rams in a variety of sizes are in museums. Over centuries with different yards and different sizes of ships maybe each one was custom moulded for each vessel.
Dang it, is a sick world wherein I am not a bzillionaire.