Grills arent to expensive, almost anything will actually work for you as long as it isnt some pos plastic thing. It is a low profile so you dont have to worry too much about the excursion of the sub hitting the grill. I know on ebay there alot of them out there for only a few bucks. That is a very clean install. I hope it sounds as good as it looks.
Quick- Got any pics of your taped covered install???? lol.
man i had some pics of this mtx 6000 sub that i had all taped up because the center piece was comming off and i didnt fell like gluing it up..it was good until it hit the low notes then...