TCM stands for "Tinted Cure Mix". They color it pink so you don't have your wife, mother-in-law, etc. mistake it for table salt. Instacure is a brand name, and Prague Powder #1 is what the old-time butchers call it. They all contain 6.25% Sodium Nitrite in a salt base with no sugar added.
A great source for these and other curing products is Allied Kenco down in Houston and you can order online. Check out www.alliedkenco.com/catalog/index.php/cPath/37_52