I don't even know if this is strictly necessary but since my powder sits in the dropper all time and I don’t pour it back into the container, I figured why not.
This design consists of a silica gel basket which holds around 23g of silica (I chose the regeneratable one which can be dried in the oven or microwave) and a top cap.
One cap for the Dillon dropper (fits into place without an O-ring like the original) and one for the xray-parts ultimate dropper (for which I transferred the original O-ring onto the new cap [rather tight fit with the O-ring]).

The silica basket is interchangeable.

Prints in place without any support.

The holes of the basket are 1mm in diameter, most silica pearls are 2-5mm so no spillage should occur.