Emergency fire ladders aren't real pricey. The hooks on the end for a window sill, work fine on branches. A bit difficult to climb. Rolls up into a small bundle.

Stick ladder is another possibility. Light easy to carry.

I picked up a retractable escape ladder from a building renovation. A bit pricey to buy new. Relatively heavy, but you can lock it closed.
http://www.jomy.eu/en-eu/Specialty-l...ctable-ladders