They will have it for sure - it's one of the staple items for a hobby shop like balsa wood and plastic glue...

Mike you just made 30 year old memories flood back - I used to run the radio control section of the largest hobby shop in town (used to fly those things back in the day when there were no computers in the radios to save you, no gyros etc). I can still clearly see the corner that held the balsa and right next to it - you guessed it - the tubes of piano wire!