Materials List:
9V Battery
Electrical Tape
Ruler
Manila Folder
Solder Iron
Piezo Buzzer
Velcro
9V Battery Connector

Measure the outside area of the battery and mark on manila folder.

Cut out and fold along lines. This makes the reusable holder for the battery.

Tape around holder with electrical tape. Battery should fit snug.

Super glue and tape Piezo Buzzer assembly to holder and you are done. Not sure if this will be too heavy for the rockets but we shall see..