I recently ordered a set of jack pads from this company: http://outdoors-for-life.com/rv.html
They make pads for industrial and emergency use, as well as RVs.
They are very substancial, and came in a nice canvas carrying bag. They should last forever, no more splitting of the old 2x12s, although I'll keep them for those occasions when one of the jacks may be in a 'hole'.
The site shows them only in black, but as you can see from the photos I'm attaching, mine came in yellow. They come in various sizes, these are 14".