I recently sold a PacSeat that I purchased used that had a pack attached. The pack had a large single compartment with additional compartments on the side. I hated it and eventually removed it. It was jusst to heavy and cumberson. Look for something light weight, sturdy, with a large opening. Some pack companies sell pack liners to help keep the inside of your pack clean. I know Bison Gear had a good one. You should be able to figure out a way to attach it. Just a thought. Good luck.