what type of coolant to use?

i have a 97 A4 2.8 Q. i'm getting ready to change my thermostat to try and fix my heater problems and i am wondering what type of coolant to use to refill the system. i have the manual and says to use some G12 kinda stuff, but i couldnt find anything like it at autozone. so is the coolant some kinda special coolant that i need to get from the dealership or did i just overlook something at the local automotive store?

http://www.blauparts.com/fluids.htm

i believe it is called pentosin, that is the brand.
or an audi or maybe a vw dlrshp.