My secret mouse fear

One of my little computer terrors is that someday I won't be able to find good quality plain three button mice any more, because everyone will have stopped making them. In fact it may already be too late to get decent USB three button mice, which worries me; although I have a stash of PS/2 ones, I may someday have to migrate to a USB-only machine.

(Searching the web is basically no help in finding out, and since I have a reasonably large stash of suitable PS/2 mice I haven't had to go out into the computer store wilds to find out.)

What I would really like is something that I am not sure is even made: a mouse with three regular buttons on top and then a scroll wheel somewhere on the side. This would handily deal with my major objection to the scroll wheel, that it gets in the way of easy and fluid use of the middle mouse button.