Can I preserve the shelf-life of a cannoli?
I think you've proved already there's only one way to do this - buy the shells "unloaded" and fill them when you get there.

Assuming the bakery people are nice, ask them to put the filling in an icing bag and refrigerate that until you arrive. Put the shells separately in a cake tin, load the shells when you get to your destination.

I'm sure that everyone concerned will understand why you want to do this...