Ultimaker 3 Tool- and Printcoreholder

Tool holder for Printcores, 3D solex nozzlecase & wrenches, cutterknife and ultimaker screwdriver

You can´t really do anything wrong here. Scale it up to 1000% and twist it till it fits on the Buildplate.
Use double sided adhesive tape to fixate it at the top-right side of your printer as seen in one of the photos