You could make a sheet of fpr easily for that. Spead about a pint of
gelcoat on a release surface, as it hardens to soft cheese, put a layer or
two of CSM wetted out with polyester resin. If you want it thin, use some
light weight CSM and a couple of layers of cloth, maybe 6 oz. After it cures
you can sand the layup down a bit to get it to an even thickness if need be.
Then pop it off the release surface. Then you will have a nice gelcoated
sheet of frp to cut to size and drill out.
For the release surface you could use some plate glass if you have any
laying around or tile board . The tile board will give you a decent surface
that may be nice enought but you could compound and buff it to any degree of
gloss you want.
Excluding the release surface this would cost about 50 bucks, give or take.

--
Ron White
Boat building web address is
www.concentric.net/~knotreel