Waterproof breathable pant that can pack into its pocket.

Patagonia
Waterproof/breathable pant for boys. The fabric and design allows for more mobility and less bulk.

Patagonia
Waterproof/breathable pant for girls. Soft, supple and stays warm even when wet.

ShedRain
A must for the inevitable tropical downpour, with a very low space profile in your backpack.