Durable Media For Outdoors

Hi there gang,
Got a new project on at my work where I've been asked to come up with assessment media (books or pamphlets)which can been used in the outdoors.

So for example - a trainer would take this assessment book or sheet out into the field on his/her mountain bike or kayak to assess a trainee on practical stuff.

We currently have notebooks with waterproof paper that can be written on with Biro pen, but other then that, I don't know where to start looking for this type of printed media! Any one heard of this kind of stuff?