3 versions, one modeled as original but plastic will not like the twist after the notch. The better way is the NO NOTCH version.
The no-notch version printed in white or reflective shiny silver PLA is probably the best choice. You can also print in black or any opaque and pray paint the inside with white or a chrome shiny paint.
A bulk package of 25 CD/DVD has a plastic lid that press-fits.
A cloth, T-shirt, or white plastic grocery bag and a rubber band also work as a diffuser... does a Yellow shirt make warm light? green or blue work?
There is a third reflector body if you have clear PETG and print it HOT (245-255 first few layers and DRY the filament first - toaster over 150F ~4 hrs) and print on smooth glass... it may come out good! It may stick and break your glass too, YMMV.
The Light-Exit side is .6mm thick , only 2 or 3 layers - I would print .3mm layers for strength. And print any of these with 3 walls.
Godox didn't send a reflector with my new 200, so I spent too much time measuring my other one :)
Edit: Originally I made this an extra 20mm long.... huh? Yeah, I did. But... That works well being like a "Fong" cap on a flash, so Ieft the +20mm version on here also.
Check back for updates - I will probably make something cooler to fit the front rectangular body batter - dunno how durable this will be - let me know, photogs!
STEP files included so you can mod it too. Peace!