I would look for companies that make outdoor shades and indoor shades. I bet they are more used to dealing with large sizes. I linked to one below. I have no experience with them or affiliation, they were just high on the list of google results when I searched. They have shades that cover garage bays, though, so might have what you are looking for.

Here is a link that might be useful: Outdoor and indoor shade manufacturer

Thanks - that was helpful. Found some local suppliers.