Most classes will allow you to wear a harness as long as it has a d-ring in the front. The "easy walk" harness is sold lots of places. It looks like the one in the first picture - you can get much smaller ones! The second picture is our favorite. Chattiesmom, a YT member, custom makes them to fit your dog. They have a d-ring in the front for class and in the back for "normal" walking. They are absolutely the best and my classes have no problem with Sadie wearing them. Check them out:
http://www.yorkietalk.com/forums/yor...elections.html