Source for Shrink Tubing?

I terminated several pairs of speaker cables with banana connectors and want to add shrink tubing at the union of the connectors and cable.  I am looking for 3:1 shrink tubing in both black and red in 1/2" diameter.  I figure 3' of it would meet my needs.  I found a few sellers on-line, but either they require a minimum dollar purchase or the smallest quantity they offer is far more than my need.  Can somebody recommend a source for such a small quantity?   Thanks very much.