You can buy thin acrylic at Home Depot. Cut it in strips and heat it with a lighter to bend it.
It will depend on what PH
you use but there are many ways to do it. I use zip ties and plastic hooks that come in mini blinds. I save misc. stuff so I normally look through my junk parts to build stuff. My canopy sits on the bracket to hold it down and you don't see it on the outside of the tank.
I have made brackets for my floats on the top off system I use with thin acrylic. I can't remember who sells the brackets but it was someone on RC. Maybe do a google search. I know I saw them but it has been awhile.
*180 gal Display, 100 gal basement sump, 33 gal refugium, 3x250 MH, 2x160 VHO actinics, zoos, some softies, LPS & lots of acros and other SPS.
*100 gal prop tank plumbed into main system w/ 2x96 PC lights and 1x150 MH,