Got a fair price on ebay on a couple of Sailor 21s. Love them, but modern converters seem to fit only in theory.

Cutting them down works, but also makes it nearly impossible to advance or retract, because there's no leverage on the screw that moves the plunger.

Am I missing an obvious source here?

Edit: They can be made to unscrew if a syringe is used to push the plunger up consistently, there's just enough to grab onto. Still not ideal, but...