If you have a Costco nearby I highly suggest checking out the High Sierra hydration pack they have there. I don't know how good the resovoir system is, but it does come with insulated tubing and a nice big opening for refilling. The pack has a lot of nice features like mesh shoulder straps, sternum strap, waist strap that can be concealed when not in use, zip up gear net that is big enough to hold a helmet, airflow on the back to help keep you cooler, expandable main compartment and a strap on the back that'll hold a blinky light. For $20 it is a pretty good deal!