Hi Mark, iv'e just replaced the rubber feet on my ZB. Bought them from a local stall trader (Wimborne market) @ 20p each

. Any good shoe repair or hardware shops usually have a selection (8mm > 35mm) of rubbers for walking canes / zimmer frames etc

. usually at a fraction of the cost from a music shop. Good idea to take a leg with you to check for correct size. Hope that helps.
ZB Custom S10 3+4, DD3 Digi delay, ZB vol. pedal. Peavey Nashville 400