Proviz are the masters of reflective sportswear, and this is their latest commuting backpack. The Reflect360 offers a 10L capacity, a mesh back ventilation system and four pockets. There are also adjustable waist and chest straps.
Buy from provizsports.com
The 18L Endurance Backpack offers hydration bladder compatibility and includes an internal mesh pocket for phone and keys. There are also open pockets on the sides for water bottles, chest and waist straps, and a choice of colours.
Buy from www.asos.com
The Agile 6 will handle both your commute and ventures into the trails, with a harness that flows over the shoulders to limit the bag moving on the run. There are pockets on the straps for the two included bottles, an air mesh back and a helmet loop.