I'm with Boing_737 - any half-decent stationary shop will be able to sell you a non-permanent marker which can be wiped off with a damp tissue. Pencils scratch the plastic, and permanent markers are a pain to clean off - non-permanent is the way to go!
Papis - I'm pretty sure there are plenty of digital versions out there, I'd try looking through the Transair catalogue or similar? As for being approved - I don't think you need any approval to use any device for flight planning. The only exception is for exams, and no they're not approved for exams.
FFF
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