Old thread, but posting this here in case it might be useful to anyone else.
I had this same problem even with the "high end" consumer ironing boards.
A thicker pad wasn't really helping: I'd still eventually get the "grill" pattern from the metal board, the thicker pad was making it harder to press clothes (because it could be compressed more), and the thicker pad absorbed more water from steam (which would eventually make the pad smell).
My solution was to layer the metal board with plastic screening. I used some rigid "plastic canvas" made for cross stitching, found at a craft shop (http://www.joann.com/plastic-canvas-13-1-4-x22-clear/xprd1144449/). I cut it to size and taped it down on the edges. On top of that I put a thin felt pad and then the cloth top sheet.
The end result is a thin & flat pad that doesn't transfer a pattern to the clothing, and is very permeable to steam.