The 7Artisans 4mm f/2.8 was just announced, and it should be available on their Amazon store soon.
Featuring a one-of-a-kind 225° field of view, 7artisans 4mm f/2.8 fisheye lens can create a circular fisheye perspective on Micro Four Thirds (M43) & APS-C cameras. Photographers can create a 360° full panorama image with a minimum of 2-3 shots. The lens weight only 7.09 oz (201g) which makes it extremely portable and allows photographers to have creative shots anywhere, anytime. The lens can also be mounted on DJI Inspire X5 cameras for creating a unique perspective you have never seen before.
via Photorumors
