Any of the major wholesale distributers for commercial greenhouse equipment can help.
BWI Companies and Hummert International. Both can handle this type of equipment. There are many others.

Not everything is on the web, yet.

This is my first post however I have read many post. I have a HFGH bought last Febuary. With pic from this forum I was able to put it together . That said I have a question. I accuired a swimming pool insulation cover. I would like your opion on putting it on . Will it be to heavy when we get our usual ice storms here (Texas)? Robby

Thanks Mylu. I'll look into those. When we were at the mfg that may do our solarium/greenhouse, they have made to fit "curtains" for shading that run in tracts in between the frames. Really cool. Also really really really expensive!! The salesperson actually suggested that I forget the shade curtains because they are so outrageously expensive. Looking at them I think it would not be too difficult to fashion your own for a lot less money. Could probably do the same with the thermal blanket.

Jaroban, I'm not at all familiar with HFGH but there seems to be billions who are. You may want to put out a separate post for your question.