Update: I had another go at finding that original photo, and I think it was the one that appears with Richard Gain's ducted fan for Mendel90: https://pinshape.com/items/4488-3d-printed-low-profile-ducted-fan-for-mendel90-with-e3dv4-hot-end

I saw this design in a random photo (which of course I can't find again), but couldn't find an stl for it. It looked like an interesting thing to print so I created a model in OnShape:

https://cad.onshape.com/documents/62fc907018bdbbbd171f23c2/w/481169a229d6a1f2a706b3fd/e/0e2eea80694bd9a8650d3542

I found it quite difficult to print, the overhangs are about 35 degrees and they have a tendency to curl, and the bed contact area isn't very big. But it did eventually work without supports, although it's not the cleanest print I've made.