He might already have them, but float bags are a great bit of safety gear that can sometimes get overlooked when more "essential" gear eats up all of the funding. Float bags go in the back of the boat & are filled with air so if the paddler ends up swimming the boat is easier to recover. If you can find out what boat he has an outfitter can point you in the right direction of which size to buy.
dry bag- I have a stoic that works great and has a valve for controlling how much air is in the bag.
Your brother's a pretty lucky guy