RWS/Diana 54

The Diana Catalog shows the standard 54 Air King along with that laminate one. US retailers? Safest bet is likely emailing their Customer Service and asking if they are or planning to, ordering, carrying them and if they can give you a ballpark on when.

As far as the RWS connection, that's long gone as RWS and Diana parted ways and RWS no longer imports any Diana rifles with their RWS logo on them.