I have tried to locate the reflectix at Lowes and Home Depot but came up empty. Is there any other place to locate the material in rolls?
Yes, I'm sure lots of places have it, but I've seen
it at Home Depot, and it's shown on their web site (use the search box with just the keyword "reflectix"). It may be that some individual stores don't have it, but it seems more likely to me that it was just in a strange place (which often happens at Home Depot...), or they are carrying an alternate brand.