O-rings are great with noise because they take out a lot of the higher overtones. There are pads, too, I bought some from Leopold, and they are good noise reducers as well, maybe better than O-rings, but aren't as crisp at the bottom.
Also, there are sounds going down and coming back up, mostly these remedies only attenuate the down stroke. And, depending on how resonant your desk is, a rubber pad underneath can be a significant help.
I don't know which supplier, but I think that there is at least one company that gives serious discounts to active duty military personnel.