The space for beans in the Autentica is small enough for it to constantly make me want to top it up. To overcome this, I've crafted this large hopper which can just be push-fit into the top. The original lid then fits on top. The original lid has a hole in it aligned with the place which alledgedly is for putting pre-ground coffee in, but I just don't use that. In any case, the hole need filling to prevent dust getting into the coffee, so that's what the plug is for.
Note: The pictured hopper holds about half a kilogram.
If you wish to modify the design, it's on OnShape here: