Ergonomic Buttons for Space Navigator

The stock buttons on the space navigator bug me. They take too much force to press for their size (they're uncomfortable) and you have to squeeze the whole device to use them - you have to press them horizontally. This is an attempt to fix these issues.
1. I want the buttons to have a much larger surface area - to make them less pointy and thus more comfortable to press.
2. I want the buttons to actuate vertically, so that the actuation force is toward the desk rather than trying to slide th