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Here's another: The old-style Waterman ballpoints with the very long spring and a flared end. Must de Cartier refills work fine in them, at about $10 to $13 each, or a much-less-costly Cross refill can be made to work by cutting it down to length and flaring the end; nice if you have the flaring tool!

A slightly simpler method of using a non-pressurized (important!) Cross refill: pull off the threaded plastic cap, cut off .875 inch or 22 mm from that end, push the cap back on, and sand/shave the outer diameter of the cap until it moves smoothly into the pen's barrel. The cap takes the place of the flared end very nicely.