Holy foam

I've had success getting black pipe (natural gas from Home Depot) hot and burning through some softer Wally World pad.

Just a thought.

I'll add a simple hole puncher to the list- other than that I got nothin'

If you squish the foam flat it's easier to poke a hole through it

Like you could have a plywood board with a hole. Squish foam. Poke through the hole to make hole in foam.

I think you might have some luck if you searched Google for 'Perforated Foam'

ULine has a selection of various thicknesses and widths of perforated foams. You might want to check them out here: http://www.uline.com/BL_869/Uline-Perforated-Foam-Rolls

Hope this helps!
QX

If you are serious about making holes in foam I recommend one of these:

here

One of these would be slower but less expensive:

here

Thanks for all the suggestions everybody, but I'm looking more for the stuff I've seen in some big manufatures backpack's mainly shoulder straps, and some of the stuff I've seen was also used in the back panel up against your back, the color I've seen is white, but color is of no concern.

Thanks, Jack