The original refills came from Ballograf, since Montblanc cooperated with the Swedish manufacturer at the time; they are hard to obtain in Germany but available without trouble in Vienna or directly from Ballograf in Sweden. As a workable substitute, forum members recommend a standard DIN large-capacity refill (e.g. Schneider Express 225 or Schmidt) with the rear plastic spacer snipped off and the end filed smooth so the lever mechanism still works correctly. The Schmidt refills are mentioned as the best choice in terms of quality. Penboard.de also offers an adapter for old ballpoints. Worries that snipped refills might leak are dismissed by experienced collectors as unfounded, since the writing paste is sealed by an oil layer.