I fould two web sites that had some "Juliana greenhouse" hardware for HFGH. The best site had T-bolts that you insert and twist 90 degrees into the channel aluminum studs.It aso had some hanger clips for hanging plants etc.that looked much more substantial than the Juliana brand. I liked the clip's engineering.The prices were reasonable, but the shipping was a little high: $9.00 for under a pound that could be put in an envelope.
Further, I found a site that had polyethylene gridded top material:28"by 48".They were about $9.00, and would be perfect for greenhouse bench tops.You could also clip them together to extend their length.A wood frame is a great choice, but you have to be careful with pressure treated stock in a greenhouse because of the water leeching out cupric chemicals from the pressure treatment. It will poison plants. Cedar is cool, and more friendly! E-mail me if you want the shelf top site.