Consider it an opportunity to build up your immune system by exposure to germs? Or maybe discretely use hand sanitizer after holding hands.
In answer to the original question, I’m also of the opinion that the orans posture is an invitation to hold hands, so I would just keep my hands discretely folded if I wished to avoid holding hands. I don’t frequent parishes where holding hands is common, but when I find myself in the position where somebody just grabs my hand, I “grin and bear it” for the sake of Christian charity. I don’t mind physical contact with strangers; I’m happy to shake hands with the 4 or 5 people closest to me during the sign of peace, I just don’t like hand-holding during the Our Father. If I felt uncomfortable with the physical contact itself, or was afraid of the germs which permeate our world, or was just grossed-out by the thought, I think that I would tend to avoid those who are known to be hand-grabbers, and of course, pray with my hands folded in front of me. If they proved to be unavoidable (such as a parish full of such people), I would probably try to sit (or stand) in the back.