Sheaffer cartridges? It is possible, even though I'm not sure of dimensions. The only thing that can go wrong is that the plastic cracks in the refill.
Maybe a Parker will also work (5.3mm diam)
For the next iteration I will inmmerse the cartridge in hot water after cutting to make sure it conforms to the threading better and seals perfectly
According to this site, the Platinum cartridges may work.... (6.2mm diam)
PS I tried linking the images but webp is not allowed
Since we were snowed-in last night I checked the cartridge, after a week I still had 1/3 of ink (yay!)
However the cartridge had cracked on the threaded junction and thus it went to trash
Fortunately the Himalaya also works as an eye dropper pen and no leaks!
Back to the drawing board
Edited by titrisol, 13 March 2018 - 13:08.