+1, these help ward off cramps for me too. I leave a few in the backpack in case I get a cramp although at time out on a trail it is a bit late anyhow :|For cramps, try magnesium tablets. I went onto them daily and cramps disappeared.
I use a bladder from anaconda for $15. The good thing is you can walk into a store and actually see if it fits your bag (they sell 1.5L up to 3L in 500ml increments). Their returns policy is also pretty solid if it comes to that.Will probably test one of the ebay bladders out.