For taping feet, Elastoplast (by Beiersdorf) or Elastikon (by Johnson & Johnson) are MUCH BETTER than duct tape. These tapes are thicker than adhesive tape, they stretch to conform to difficult areas and they stick! Really well.
Buy a 2" role, cut a rectangle for your heel, and it will stay for days of miles.
I've carried a roll to blisterproof every outing for seven years (because moleskin never held.) You usually can find Elastoplast or Elastikon at a podiatric supply house or sometimes at an independent type of pharmacy in the medical/clinical part of town. (Chains like Walgreen's usually don't have it)
Here are some web-blurbs:
ELASTIKON Elastic Tape by Johnson & Johnson
Elastikon elastic tape is made of a high twist, cotton elastic cloth tape with a rubber based adhesive. It is best used where pressure dressings requiring elasticity are needed or can be used for support strapping, fractures, muscle injuries, knees, elbows, and shoulders. Natural rubber backing, not latex free.
http://www.allegromedical.com/Home/moreinfo.asp?C=541&S=3784&M=15077&P=191128 Elastoplast - Comfortable yet rugged, pure cotton adhesive bandage that provides excellent support while its stretchability allows for freedom of movement—it won’t slip, bunch up or gap and needs no clips.
http://www.alertservices.com/images/BSNELAST.jpghttp://www.google.com/search?num=20&...kon+elastoplast