Bounce flash using your camera’s integral unit. This one could have some merit but it costs 30 dollars - feel a bit of DIY coming on. I put a piece of tracing paper over mine to distribute the light more evenly.
I can’t imagine it’s going to chuck out much light, I think your idea is better Neil, I often make my own light modifiers out of bits of card and gaffa tape, the beauty of them is that they are cheap and customised for the job in hand And dare I say, often better than what you could buy!
This was shot with a ring flash diy job made from tupperware and foil and few bits of gaffa tape.