Over the years, I've found that there are two "off the shelf" alternatives to the original padding, that keep rising to the surface.
The first is the Dutch Military sleeping roll
(described in this thread)
I also believe it was mentioned here (back in 2006) that Mr. English spoke of the original armor padding, during the "Alien Encounter" held at the Leicester Space Museum.
He stated that the original armor padding was made from a foam bed mat.
(Another good reason to lean toward the Dutch roll)
I believe that after it is split in half, the dutch military sleeping mat is the correct thickness.... Although the squares are a few mm. too large.
From what I understand, the original measurments are:
Squares - (6.35mm)
Thickness - (7.94mm)
Sleeping roll:
Squares - (10mm)
Thickness - (16.5mm)
A few links I've collected for finding the Dutch sleeping mat.
(Although I have not checked them in quite a while)
http://www.exarmy.co.uk
[Product Code: K28B]
http://www.genuinearmysurplus.co.uk
[Dutch Roll Mat]
http://www.asmc.de
[Product number: 32732]
* Although not quite as accurate, the second item that might make a decent alternative is a cross pattern Yoga mat.
(They have also been mentioned here in the past)
The "Yoga Essentials Mat"
Available from:
www.gaiam.com
...Seems to be a good candidate.
The color(s) to choose are the dark green, called "Leaf",
or the lighter green, called "Fern".
Another advantage of the Essentials Mat, is that they are
readily available and sold in many Taget® Stores.