If you don't find a solution an alternative would be to use Sony APSC instead. There is a Sony fisheye converter that fits both the 16mm and 20mm pancake lenses with autofocus.
I just got it for the 20mm and it turns it into a 13mm fisheye. I will actually prefer this to a real 180 degree 7.5mm fisheye lens as I like to use fisheye occasionally for street photography (have to get too close with a 7.5mm lens).
It can all be bought very cheaply e.g. a used A6000, used lenses and the fisheye converter was only something like $40 used (costs more for the black version but I am just going to tape over the silver on mine).

Or if sticking with Fujifilm and going with manual focus, I can vouch for the 7Artisans 7.5mm f2.8 which is very good for the price, much cheaper than the Samyang. It has very close focusing or there is a 2nd version with improved optics (like less CA) and no close focus. I would set it and forget once I found where infinity was on the barrel.
The 10mm f5.6 Pergear is a piece of junk. Mine was only ~$40 and not really worth any more. Skip it, very poor optics, sounds like their f8 bodycap one may be better. The 7Artisans is the way to go for a proper fisheye with surprisingly good optics for ~$135, unless you want to pay double for the Samyang which is stetosonic (or something? That makes faces bulge less).
Edit: tried the Sony yesterday and it is very nice having autofocus for close up subjects like animals. I used to miss regularly with the Pergear which became frustrating. There is definitely a gap in Fuji's line-up for an autofocus fisheye, or even just a converter for a wide lens like the 14mm or 16mm. The Sony converter is so cheap that it must be a very small market