Condor pack and a couple of cheap non-rated links. I think this pack was about $25, but you can do this with any pack. The one on the back of my driver's seat is an old Army surplus map bag that I picked up for about $10.
This one holds itself open like a little tray table and carries my backup ham kit, license, notebook, and band plan.
I also added this LED round to the inside of my tailgate
The switch came with some lights and I didn't need two of them, it was scavenged for this project.
Rather pleased with the results.