Hi there, I'm looking for a decent trackball. But not a tiny little one, like the ones that you have on the latest mouses. I'm looking for a simple square block, with a big big trackball in it and just 2 or 4 knobs. With big, I mean.. like 3" or 4" or somth. Does this kind of trackball exist? If yes, does anyone use it inhere? or can anyone tell me how and where I can get one?