The good news is that there aren't proprietary electrons yet so if you can get something that fits and gives the right voltage you should be fine.
The battery maker is under NDA, I'm sure Mont Blanc made sure you're not going to find something on AliExpress.
And, yeah, I hate to blame the victim here, but who buys high-tech electronics from a maker of...fountain pens? (And maker of fine fragrances, too. sigh)
Relative to what you can buy from other more reputable brands for a similar price point, it's actually not great. Nib usually needs work due to poor QC, they creak, and they're just generally a lacking experience. I'm also not endorsing spending a grand on a mass-produced pen, but there's a sensible middle ground of not buying junk nor overpaying for something that doesn't enhance your writing experience. Equally, price isn't a reliable indicator of quality.
Yes, the Jinhao's of the fountain pen market make pretty decent pens, but that's not a fair comparison. That's like saying a Timex and a Rolex both tell time just as well, so why does Rolex exist?
The battery maker is under NDA, I'm sure Mont Blanc made sure you're not going to find something on AliExpress.
And, yeah, I hate to blame the victim here, but who buys high-tech electronics from a maker of...fountain pens? (And maker of fine fragrances, too. sigh)