Here is the stuff I use. It is "Medical Grade" which is the highest quality. A $10 pack will outfit 20 pipes or so, so why not get the best? You can get plain food grade for $8 a pack, though. They shrink with a hair dryer or heat gun or even a few passes with a lighter, but you have to be VERY careful with a butane lighter or it will melt. They don't impart any more taste than a vulcanite bit will.
http://www.grainger.com/Grainger/INSULTAB-Heat-Shrink-Tubing-4WMU6?Pid=search