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. Please take a look at my selection and let me know how many feet you need. This 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 2:1 ratio and black in color. I buy from several different suppliers so its all different brands, but pretty good stuff. Same shrink I use in my own installs. 
 
This 3/8" heat shrink works well on 8 AWG wire.