Installing an aftermarket video system?

I just decided to add a mobile video system to my 2002 Trailblazer LS 2WD. Does anybody know where I could find a switched aux power to tap into under the rear seat?

I removed the spare tire tools and used the two studs to bolt my DVD player brackets to, fits nicely under the rear seat, now I just need switched power.

VIN 1GNDS13S822421574