I have some old technical pens that I have been wanting to use, but due to neglect, some of them are fairly crusty and in need of some tender loving care. Back when Koh-I-Noor and Rotring Rapidographs were my illustrative weapons of choice, I used to rely on this excellent container of Higgins Pen Cleaner. It had a retrieving tray in the bottom similar to jewelry cleaner. Drop the nibs in the tray; submerge the tray into the soapy liquid and come back the next day. All that was required is that the parts were rinsed, dried and were as good as new to draw again.
While searching for tools for a plumbing project, my missing jar of pen cleaner did turn up, but it was at least a decade old. The liquid within had become a gelatinous black and blue blob.
A search online and in brick and mortar stores came up dry. There are pen cleaners available, but they are small, pricey and just not the same thing. Art supplies are a niche market, and the pen cleaner is a tiny niche within that niche.
There are some DIY solutions that I will chase down and try on my own. Stay tuned!