Did you check where the puncture was on the tube? Reference the puncture to see if you have either something sticking through the tire or possibly the rim tape is not doing it's job - again depends where the puncture is.
As far as tubes if your lbs does not stock, they should be available online. With a handle like 50 Mission Cap sounds like your from Canada - try Mountain Equipment Co-op (mec.ca) carries a 26 x 1.25 - 1.5 tube.