Just finished a shulker farm so the storage doesn't become a problem in the near future.
The farm is located at around x: 1960 z: 440 (it used to be a city...). If you go through the end gateway with the sandstone stairs you come out in a gateway that is in a straight line to the west of the farm, just keep going east and you'll find it. It is easier with an elytra, but in the future I'll be building a rail line to get there easily.
I'm not sure about the rates, but it should produce a good amount of shells. You are welcomed to take any shells you need and/or afk here to produce some more.
