Get a couple of Titanic posters. One on your front and one on your back, Titanic sandwich or whatever.
Maritime Museum may have some if nowhere else has.
Telephone: 0151 478 4499http://www.liverpoolmuseums.org.uk/maritime/exhibitions/sail-away/
Or make a big Menu. https://www.google.co.uk/search?q=titani...enu+first+class
Or a bow tie (which you will have) and a violin
Mersey Ferries may have some imitation Captain Hats Pier Head, Georges Pierhead, Liverpool L3 1DP
0151 639 0609. They'd probably send it over to this side if you asked them for you to collect. Might also have other stuff.