Rear Seat Delete for speakers

I was suggested to get a seat delete for my 03 GT because my Bandpass box (speakers) are sitting on top of the back seats. It's a heavy box, and I couldn't fit it in the trunk. Anybody know where I can get a good deal on a kit? Does anyone have pics of a kit installed? Will it accomodate my box and allow me to anchor it so it doesn't move? Does it cover the gap between the back seat and the trunk? Any help would be greatly appreciated. I now realize that it can be a safety hazard and I want to do something about it promptly.

03 Ford Mustang GT Premium 4R70W
UPR O/R X-Pipie
Flowmaster 40'S
UPR CAI
SS Bumper Inserts
Bullitt fuel door
Visonik Bandpass w/ Mach 460 combined