I get my greenhouse plastic from ACF Greenhouses because I can get it cut to the size I need. Saves $$$ on wasted plastic. They have rolls also if your greenhouse is bigger.
Another option would be to use Solawrap greenhouse bubble film to cover the side walls. It is insulated, does not need inflation, and can be used with roll-up sides.
https://www.acfgreenhouses.com/solawrap-greenhouse-film
