In reply to TheDrunkenBakers:
There are various options for carrying water - bladder ( from 1L to 3L ) in the backpack, hard bottles on the front, soft flasks on the front.
The advantage of a bladder is that it is out of the way on your back, disadvantage is you have no idea how much you have left ( apart from guess by weight/feel ), and they are a hassle to fill up in the middle of a long run if you need to.
The advantage of bottles/flasks on the front of the shoulder straps is that you know exactly how much you have left, and they are easy to get out and fill up again if needed. The advantage of soft flasks over bottles is that the soft flasks collapse as you suck the water out of them, so the water doesn't slosh around as much as it does in hard bottles.
Take a look at all the options Salomon offer -
http://www.salomon.com/uk/men/backpacks?sport=running
They do lots with different ( non water ) carrying capacities , from just 2L up to about 20L. Some with just the front flasks, some with just the rear bladder.
Other brands like Inov8, Ultimate Direction, Nathan etc do similar, check out their websites.
A lot of these "vests" are pretty expensive, if you're on a budget, check out the Decathlon one
https://www.decathlon.co.uk/mens-trail-bag-id_8312245.html It only comes with a bladder for the back, but if you think you'd prefer bottles/flasks you could buy them separately and still be cheaper than the Salomon/UD/Inov8 equivalent, assuming the carrying capacity of the Decathlon one met your requirements.