Here is a wearable chair that you can use anywhere to give your feet a break. The Ofrees Wearable Chair lets you maintain a good posture while sitting down. It fits in a backpack when you are done. Simply secure the lap belt around your waist, buckle the clips around your legs, place your legs into gaiters and tighten.
The Ofrees wearable chair is available in various sizes (2XL,XL,L,M,S). Costs under $900 at this time.