I got this one recently to do exactly the same thing on my Ultegra 8100:
It definitely came with the ‘adapter’ that goes between the cup and the reservoir port on top of the shifter. The only other things I bought were a set of Shimano brake hose vice blocks to help with cutting as well as setting the barb:
Amazon.com : SHIMANO Tubing Vise Blocks, TL-BH61 pr : Bike Repair Tools : Sports & Outdoors
And new genuine Shimano brake hose barbs and olives for each line I had to shorten:
Amazon.com : SHIMANO SM-BH90 Olive and Connecting Insert : Bike Brake Hoses : Sports & Outdoors