Glass blocks (for privacy or decorative walls and window openings) are
usually 3" and 4" wide.

According to the following statement (which is apparently 6 years old),
it would seem that 2" blocks should be some-what common today:

----------------------
Building Products, March-April, 2004 by Stephanie Herzfeld

Glass block manufacturers are keeping pace with acrylic, introducing
lighter, 2-inch-thick block windows,

"It's still heavier than acrylic, but it's a very manageable weight,"
says Kurt Hodson, general manager of the glass block maker Pacific
Accent. Two-inch-thick glass block weighs one-third less than
traditional 3-inch-thick glass block. Acrylic block weighs 75 percent
less than all glass blocks, manufacturers say.

Hodson notes that 2-inch thick block is overtaking traditional 3- and
4-inch-thick block and more companies are offering it, (...)

http://tinyurl.com/28nj4x5
----------------------

What I can find on the net are pre-fab window products using 2" blocks,
one of which is known as "LightWise" - which confusingly seems to be
made by either Pittsburgh Corning or Chicago Glass:

http://www.chicagoglassblocks.com/news_lwise.php
http://www.glassblockdesigns.com/GB-277.pdf

And another 2" prefab window system with the brand name "Hy Lite":

http://www.acrylicblocks4less.com/Gl...ckwindows.html

What I can't find is any evidence that anyone is making / selling 2"
glass blocks (any size, 6" x 6", 8" x 8", etc) individually (or in the
typical box-quantity of 4, 8, etc).

So - are 2" glass blocks available to the home-owner / renovator?