Hi John, thanks for your advice, much appreciated. I've looked on Ebay and Amazon but having no luck yet.Get some from Amazon and compare the quality. Check the outside diameter of the pen body carefully with a micrometer in the millimeter (mm) size for fitment.
I also bought some from Ebay that worked well for me in my old antique Roland PNC-950.
Hi Cornholio, thanks for the info, much appreciated.Those are HP pens like for the HP7475 some 40 years ago. If you want mileage and no dry-up, buy a Mimaki ball pen. They come with the latest UCJV330 for example.