I saw these at the recent Chicago Pen Show. Very clever design and simple to use. See attached link for each product including video how to use. Ink miser inserts into most standard size ink bottles to allow the very last drop into a conical device for filling. About $6.00 each. Available at many pen shops or ink suppliers.
Link to JetPens
https://www.jetpens.com/Ink-Miser-Ink-Shot-Inkwell-Clear/pd/21652