I've just read this interesting article. It's amazing to know that there is people today in hand-made carbon bulbs business.
It's a pity that there weren't any such manufacturer in Europe, because it would be very interesting to get some items, not only to my collection but for everyday use too, if such could be availables in enough quantities. But being an US based manufacturer, international shippings are very complicated, not only for logistics but for customs, duties, etc.
About voltage differences between EU and US, there is no problem because this can be solved by means of step-down transformers or even by connecting two equal lamps in series among them. Frequency differences neither is a nuisance for this use because incandescent lamps there are no other thing that resistive loads, so them can work perfectly from DC to RF without any problem.
Regards.