how about a metal cigar tube? you'd cut a hloe for the cable in the screwable top. then to store, insert the cable into the cigar tube. twist the cap on to secure.
how about one of those telephone 'winders'? they're also used for ac cords (also in vacuum cleaners). but it'd look strange glued to the side of your transducer. you'd just pull on it to extend, then pull and let go to retract.
personally, i'd just slit a hollow rubber ball, squeeze it, insert the cable, let go of tension. spaldings, are best. (anyone remember handball?). a tennis ball may work just as well. just make sure it doen't pinch it (wires) too tightly.
if it's for on the go, gerG can help you with clips.