I've got some diffusion film and can make a circle for you if you like. But, it's single use stuff only though. Once you take it off, you'll need another piece if you want to replace it.You can also experiment with a clear film cannister... If they're even still around anymore, that is... I've seen several examples of them being made into diffuser/lantern attachments for various LED/pocket torches.
I looked and it does not look like they make the wands for the E21.