I procured some heavy-duty EPDM roofing material to cut for keyboard mats.
This is the thick, 60-mil industrial variety, much thicker than similar materials such as pond liner or such that you get at Home Depot. You can see in the side photo that it is thicker than a dime or a cent, about as thick as a nickel, and slightly thinner than a quarter. This material is vaguely similar to a tire inner tube, but much thicker and stiffer.
These mats are cut individually so please specify a size in inches or centimeters, and I will custom cut it for you. Please don't say something like "the size of a HHKB2" because I may not have the item you are describing.
Consider whether you want it the exact size of your keyboard, slightly undersize (so that it does not show), or slightly oversize (so that a narrow border of black shows around the edge) by adding or subtracting 1/4" or 1 cm all around.
$8 Extra-Small - up to 12" x 4.5" (30 cm x 12 cm) for HHKB, Poker, JD40, custom very small keyboards
$10 Small - up to 14.5" x 6" (37 cm x 15 cm) for TKL "tenkeyless" -type keyboards
$12 Medium - up to 17" x 7.5" (45 cm x 20 cm) for average conventional keyboards
$13 Large - up to 19.5" x 9" (50 cm x 23 cm) for larger standard keyboards such as IBM Model M and Dell AT101 keyboards
$15 Extra-Large - up to 23" x 9.5" (60 cm x 25 cm) for oversized keyboards such as 122-key terminal boards
Send me a private message and pay via Paypal "merchandise" including postage via US Post Office domestic only.
I can ship international for an additional $10-$12 because they are surprisingly heavy. I will combine shipping for multiples.
While supplies last, I can cut larger pieces for higher prices.
This is an update of my earlier thread
http://geekhack.org/index.php?topic=54414.0