The Mystery Ranch RATS pack is the best Medic pack available on the market. The Jump version, which, as the name indicates, you can jump with, is even better (albeit quite difficult to source).
The pack is 3.2 kgs (7 lbs), for a capacity of 23L (1,405 cu inches), and dimensions of 51x30x14cm (20x12x5.5”). It is fully NIR-compliant (zippers included).