You mention plane travel, which suggests you will be flying to your destination. Honestly, I would simply walk into a local hardware store and purchase a shovel replacement handle or similar, modifying it to your taste with the saw on your multitool.

There are loads of other options. I am a fan of walking sticks such as you describe, and I have fashioned them from a) branches retrieved from trailside piles, broken mop handles, and one I found on a beach.

They will all be as sturdy or sturdier as the screw together sections of the product you feature - and much cheaper