Do you want something freestanding? are you growing in a room? Can you suspend the light from a ceiling or do you want to be able to move it around?
You could build something out of wood, PVC, pipe, etc..
To build what is in the picture, looks like you'd need (7) PVC straight connectors, (6) PVC 90 degree connectors, and (2) "T" connectors and the PVC pipe and glue.