Most of my diffuser thinking has been around non-wearable projects, where weight and rigidity and sharp corners aren’t a problem.
I didn’t find anything appropriate in my diffuser bin.
Here’s a few links that may have interesting ideas:
- Translum diffusion again. What you see on the (focussed) photo is a cheap dull - FastLED Archive - Maker Forums
- I made a wee compilation of my most nature-themed patterns, - FastLED Archive - Maker Forums
- LED diffusion experiments, some results | Details | Hackaday.io
- Pimoroni Unicorn HAT HD : ID 3580 : $34.95 : Adafruit Industries, Unique & fun DIY electronics and kits
I use Acrylite Satinice 1/8" 3mm sheets for most of my projects. You could put a rounded edge on them. They’re not flexible though, acrylic can be brittle.
I don’t have any appropriate samples to try, but I was thinking a translucent silicone mat might meet your criteria.
Here’s a picture of some thin packing foam from a recent Aliexpress order. It tears easily from the edge, so maybe not as robust as you’d need.
Think about layering something soft under something more rigid, like a clear file folder that will hold its shape, and potentially hold the diffuser in place.