Hi Wofgang, in addition to Backscatter and Retra you can try contacting Fabio Iardino the owner of Snooty. He is an Italian underwater photographer who produces optical handmade snoots for different flashes with central and offset aiming lights such as Seacam, One UW, Retra and Inon. I don't see the HF-1 listed among the models but you can give it a try. I have one of his snoots for an AOI Q1 flash and I am happy with it. Here is the link to Snooty website: https://www.snooty.it/en/home-2/ Pietro