From: Sourcebook 2011, from Composites World.
Sub-heading: Rotational Molding
Arrowhead Plastic Engineering (765) 286-0533
Centro Incorporated (319) 626-3200
Composite Specialties (949) 645-7032
Global Composite Solutions, Ltd. (781) 871-3700
McClarin Plastics Inc. (717) 637-2241
Quicksilver Innovations (208) 549-5101
These may be firms that fabricate composite parts via rotomolding, but I thought the list might provide some leads to your FG mold question or to an actual FG mold makers.
Hope this helps,