I buy rolls of heat shrink in bulk. Several different sizes, for my own installs. I can cut it off by the foot for your installs. I sell this heat shrink by the foot.
 
The quantity of feet will be cut off in one continous cut and not individual feet.

This heat shrink is 2:1 ratio and black in color. It works well for soldering head units and small gauge (16-18g) wires.