This is a dive slate. you write on it under water. the dimensions for it are 3.5"X6" there is a 0.25" diameter hole in the corner for fixing it to your gear/pencil attachment. I dont believe in paying for a piece of plastic that I can just print.

Instructions:

print it in white abs (or glow in the dark maybe?) and acetone wash the top of it. the bottom should be smooth enough to write on right off the bed.

LET ME KNOW HOW IT GOES.