If you want something larger then you need to go to a greenhouse company..
IGC has larger/wider
Cheaper way to go is with a steel tube frame hoop house and inflated double layer 4 yr poly film. http://www.greenhousemegastore.com/R...ctinfo/CG-RAN/
for example a 30' wide 36' long steel frame is $3-4k depending on which load rating you go with. Poly film is only a few hundred $. vs the 12' x 12' with 6m poly carbonate for $4k.. polycarbonate is nice but adds alot of $$