One idea is to watch for a deal on an old Thunderbass 1-15 cabinet. I just measured the dimension of the Maverick grill and the Thunderbass cab and they are both 23" tall. The Thunderbass cloth could be used for the Maverick grill.
Another idea would be to approximate it by purchasing a black grill that mimics the Guild amp and then apply a light spray if white paint to the cloth.
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