Eduard (www.eduard.cz) makes 1/72 scale PE sets and PE tracks for at least the PzKpfw III and Cromwell. Tracks-n-Troops (http://www.tracks-n-troops.com/) carries a lot of Braille scale stuff. I've ordered the PE set for the Roden JS3, Revell M1A1HA and several aluminum barrels.
Here is a site dedicated to 1/72 scale military modeling: http://www.ontheway.us/default.htm