Thanks for answering jdgm!
As a matter of fact I did email Schaller a couple of days ago and the owner, Dr. Lars Bünning, answered me himself! They don't have any record of the screws or anything.
I've ordered a thread gauge and digital calipers so I can figure out what screws and nuts these are myself. Once I have the dimensions I'll post that info here for other people to reference in case anyone else needs this info. Hopefully I'll also be able to use the info for finding a replacements, if they exist.