Solutions for long sessions and downwinders?

What are your gear solutions and tricks to bring stuff along on long sessions or downwinders?

For example:
Water bottle, phone, key, money and creditcard, food and snacks, sun cream, pump, gopro

In Brazil I did sometimes downwinders or trips to a remote lagoon where I spent multiple hours on the water or only had one-way buggy transfer where I could not leave stuff behind. I used a waterproof drybag, but this is not really comfortable for riding.

My new ideas so far:
Trail running vest
Sticking some kind of holder to the twintip board
Somhow mounting a sling bag to the harness

What have you tried, what works, what doesn't work?