We have featured a bunch of pop up flash diffused before as a poorman’s alternative to getting some nice diffused light. Build materials ranged from cardboard, through cloth hanger and headphone packaging.
The idea is that light coming of the pop up flash will hit the diffusion panel and then two things can happen:
1. Flash will appear bigger since it is coming from the scrim so light will be softer and/or
2. light will be scattered over the room and bounced back from ceiling and walls, again provided softer light.
All those hacks come with a price, they eat light like bears eat honey so be aware.