The labels must be heat shrink material. If possible, can the labels be printed off of a ink-jet printer or other type printer?
And you would feed lengths of 1/2" diameter round heat shrink through a printer how? :cheesy:
Seriously though, a cheaper and probably more flexible alternative to printing on the heat shrink itself would be to use printer-feedable sheets of adhesive cable labels and then shrink a piece of clear heat shrink over those. Brady makes a wide range of these labels and labelling accessories.