I need to find manufacturers and vendors for LED video wall products. 
The important distinction here is that they are LED video walls and
not CRT or LCD video walls.

The products I am looking for are used to back rock concerts, big
conventions, etc and are often modular systems of panels that can
interlink, both physically and virtually.  The Experience Music
Project in Seattle has several of these walls installed, in various
sizes.  I am looking for a product that has thousands of small,
discreet units of 3 LEDs (Red, Green, Blue).

Ultimately I need pricing for this product, but more important now
would be to identify the top manufacturers and vendors.

You might try http://www.lighthouse-tech.com/ - they are one of the
world's leading manufacturers.  Oddly enough, I was talking to one of
their salesmen on the telephone a couple of days ago.  He said "the
prices will make you feel ill".  He was right.

Try Phillips, they seem to be the lead manufacturer of the LED and put
me intouch with the suppliers who are developing their products

http://www.philips.co.uk