Where can i find a sub box for my 2004 Chevy Silverado 1500?

[LSU_Student17]

I'm new to the audio world, and im getting my first system put in my truck. ive got my amp, subs, and such..but im having trouble finding the box i want. im looking for a dual sub box cut for 8" subs with space for an amp in-between. it also needs to go underneath the backseat. ive searched around a few websites but im still new and inexperienced. any help would be greatly appreciated guys, thanks.
i forgot to mention that its an extended cab also.

 

[Eskimomann209]

Best place is our local audio shop or have someone make it custom

internet is ridiculous low quality and high shipping

ALWAYS check local before turning to the internet

I WAS IN THE MARKET FOR ABOUT TWO MONTHS