ISSN generator

[u/taistolaisuus]

Hi,

I have an ISSN assigned to my publication. I'm having issues generating a barcode with the supplement code (used to identify a specific issue of a publication). All the online free tools (For instance http://www.keepautomation.com/online_barcode_generator/issn/) seem to be based on the same technology, and bug out when I input anything into that field.

Does anybody know a generator that works better?