The Wow Pen Joy mouse allows most of the weight to rest on the bottom outside palm heel of the hand and the hand drapes around the mouse with very little actual pressure anywhere.
True, you are pushing it around with the inside of the palm and interior face of the thumb, but only enough pressure to overcome friction.
These are often considered too slow to be good gaming mice, but for general use, I love them.
PS - If you have a soldering iron you can easily upgrade them to lighter switches.