Thanks for all of the responses. I know how I am going to handle the logistics of this now.
I will buy a bottle from our local grocer (glass bottles only). I will go to our local liquor store and get a wine thingy.

Then wrap in a couple of ziploc bags, then bubble wrap. That stuff is expensive and I don't want broken glass or syrup in my luggage, let alone someone else's.
I will pack it in our checked luggage for the flight. We are staying the night at AS Sports before the cruise, so will unpack the syrup and carry on board.
Sometimes I just need someone to point out the obvious solution.