at my husband's work, there is a huge amount of women who deal with this on a regular basis. What his company has told them to do is when you are approached by someone you cannot or don't wish to shake hands with, take your right hand, place it at the base of your throat (not your chest!) and slightly bend your head in acknowledgement of the other person's greeting. Most people will not take offense at this but respect your wishes.

If you pick up a starving dog and make him prosperous, he will not bite you; that is the main difference between a dog and man.
-Mark Twain-