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

This heat shrink is 5/8"  2:1 ratio and comes in black. Same shrink I use in my own installs.