I use one from Argos ??9.99 and holds 1.5 litres which is sufficient for a 20 mile run. It is a mini rucksack as well so holds gels, bars, keys, toilet paper, lightweight waterproofs, etc. easy to fill. Only downside and this may be with all hydration systems, is that the water slashes around but this is only a sound problem as it does not effect running. At ??9.99 why not give it a try. Mines 2 years old and going strong.
I just phoned and only had to wait a couple of minutes and it was cancelled within a minute without any fuss. You don't need your subscription number only your name and other address/telephone details. Easy peasy.
I read this weekend that Hearst publications that publish Runners World have a global policy to charge separately for paper and digital magazines. While I like the magazine this has ped me off and on reflection and as I probably only read a small portion of it I'm going to cancel the magazine completely and save some money