Hi, everybody. I'm new here but not new to macro photography. I have experimented with many rigs to diffuse light from a flash. Lighting an immobile specimen in the macro studio is fairly easy, but getting good light on a living, possibly moving specimen with a handheld rig is more challenging.
Some things that I have learned from my trials is that any handheld rig does not fit all shooting situations, that the best rig I can contrive still has compromises, and that simple is better... and importantly, that a quite satisfactory system for most situations can be made easily and cheaply.
Currently I use an on-camera Speedlite directed to a fan-shaped diffuser made out of a sheet of translucent stationery affixed to the end of the lens. This arrangement eliminates cables and brackets. A snoot with a reflective interior extends from the flash head to the edge of the diffuser. The snoot boosts the light by about a stop, plus makes the assembly stable to wind gusts.
The diffuser and snoot store flat and go anywhere.
I have seen variations of this scheme here and there used by many over the years. A photo of my setup follows as well as an example photo. I'm posting more photos to the macro thread.