First off, your boat looks gorgeous for an '86, from what can be seen of it in that picture.
Anyway, that ladder design is somewhat generic and was found on many boats of varying makes and models which did not have swim platforms attached. Try searching eBay, greatlakesskipper and so on for "boarding ladder" and you may find something useable. Aerocraft probably outsourced it from a third party manufacturer anyway.
What broke on yours? Maybe it could be repaired. Or did something fall off, and is now resting under the waves?