I have a black tower and I put some black peel-and-stick "Sano pad" on the contact points. It works great and is much less conspicuous than wrapping the whole pipe with foam.
Depending on the color of your tower, you could try some of that GatorGrip stuff or get some padding from this place: http://www.hydroturf.com/pwc_matcolors.php
I think it's similar to the stuff I used but it comes in lots of colors.
If you have a black tower, you could try Sano Sports: http://www.sanosports.com/
I just got some scraps from their place here in Austin but that was before they had a website and stuff.