An option if you have a router is you can make a grill out of MDF. The thickness of the grill will depend on if the sub is flush mounted or surface amounted. Mine were surface mounted so the grill frame is 1.5" thick.
http://www.hometheatershack.com/for...creative-sound-solutions-sdx10-sub-kit-2.html
http://www.hometheatershack.com/for...creative-sound-solutions-sdx10-sub-kit-2.html