I didn't see similar durable bags sold anywhere so I decided to make a few to try protecting items in the pack/outside the pack from stakes and axe head as a Winter project. They are assembled with a double layer at the bottom for extra gear protection. The fabric is 1000D Cordura from ripstopbytheroll. 1" nylon webbing is used for attachment loops & 1" velcro for closure. I hope these spark somebody's creative abilities to duplicate or improve on them.

Nice project. You could also post those plans in the Do It Yourself Gear subforum.

Well sewn!

That's great looking work. Well done!