The FoldnHold company makes a tiny 6" and 4" cube that seems would be GREAT for in tree use. I saw one at a store and with 100' of line and a bag in it, it folded small enough to fit in my pocket (it does fold into a triangle). I saw that with about 10 minutes on the sewing machine I could turn it into a good in-tree tool. Unfortunately I didn't have any cash or wallet on me when I was dropping off the saw!!!
Hopefully they'll have some in stock still when I get back.