I always gone to Colin Earl surfboards in Ozy Park for foot plugs, boxes and glass, great guys to deal with and they won't rip you off. They might know about deck grip, I got mine off Squid grip in a sheet form ( about 1X2 mtrs ) that has the sticky back already on, gripped about 5 or 6 boards with it. Can't remember how much it was but per board was cheap.
If you haven't made one before don't be shy to ask questions, especially if it's a vac/bag job.
Good luck

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Whoops, sorry after posting noticed your in NSW, this is for Perth but I'll leave the post on anyway incase someone over here is interested, cheers.