ProMediaGear is a fantastic little company in the Midwest of the U.S. that makes pro tripods and associated goodies for stills and video. Back story on the company is it is run by three brothers, all engineers and two of them have years of experience in the photo and video industry.

I purchased this plate for my Sachtler fluid head which allows me to video with my Fuji GFX while keeping the Arca-Swiss plate attached to the camera. 

Thank you to Ellis Vener for suggesting this product.

I own one of their larger tripods and it is a rock-solid alternative to Gitzo and Really Right Stuff pods.

https://promediagear.com/products/pm501l-manfrotto-type-6-inch-long-qr-plate-with-arca-swiss-type-clamp-built-in-for-501pl-502-504-nitro-rc3-rc5-ng-heads?_pos=1&_sid=3689ede9c&_ss=r