Wow! How exciting! As KristiMc has said, you will probably need to sort out your own fish extender as your departure is really close!

You can do this a number of ways, and it depends on how crafty you are! You can make your own, and they can be as complex or as easy to make as you want them to be. I made ours, although ours are more complex because I designed each pocket to represent our favourite character. But in essence, our fish extender is a long piece of fabric (I know the pockets were felt, but cant remember what I used for the main bulk of the fabric). I then cut out three rectangles of felt for pockets (we are a family of three), and folded over the edges for a small seam and to keep raw edges hidden. I placed the rectangles on the main fabric, and sewed down the two sides and along the bottom (with extra reinforcing stitching at the top of the side seams), leaving the top open, and created pockets that way. Very simple way for doing it. You could probably use fusible webbing or fabric glue, but sometimes the gifts you get can be heavy and they may pull away.
Alternatively, you can 'cheat' and look at getting a hanging travel organizer. These have pockets inside and can be a nice, quick, easy solution to the extender issue if in a hurry. Most, however, do come with clear plastic pockets, so if you wanted to hidden your gifts from the prying eyes of other cruisers, you could always attach a piece of cardboard/fabric to the clear plastic pockets and cover that way. Hope I've given you some ideas. If you are a crafty person, then head to Pinterest, as there are loads of ideas on there for gifts and extenders! Enjoy!