Silent Mice for Silent PCs?

UnrefinedLayman asks: "In the quest for a silent PC, one item that seems to be consistently overlooked is the mouse: it's one of the more noisy computer components if only by virtue of the fact that it is a staccato noise. I don't notice my fans or hard drives very often, given that they are constant background sounds whose levels don't noticeably change. My mouse, on the other hand, makes a very audible *click* each time I use it, and while providing a pleasant tactile feedback, it keeps my girlfriend awake during my late-night work sessions. So I turn to the Ask Slashdot community: have you found a silent mouse for your silent PC? Numerous Google searches have yielded little. It's not as though it's impossible, as touch pads for laptops have been around for quite some time, and the iPod makes great use of the technology. ThinkGeek also sells a force-free keyboard with a "mouse replacement" built into it, but while the keyboard technology looks very promising, I prefer to stick with a mouse (not to mention something a bit cheaper). Mouse manufacturers have long touted optical mice as being superior to their trackball cousins for having no moving, mechanical parts, but it seems like they're overlooking the most obvious and still mechanical function: the buttons themselves! So what say you Slashdot? Are there force-free, truly non-mechanical and silent mice out there to be had?"