1968 Dodge dart window issue.

You can buy cupped bolts at McMaster.com that's where I bought mine for this purpose. They have just about any bolt to suit your needs. Also, note keep those original mopar door lock cylinder retainer clips, the aftermarket ones are not spring steel, they are too thick and they fail...don't ask me how I know that, I just pulled my interior door trim and replaced them with NOS mopar clips.
A cupped bolt, never heard of that. The metal washer around the bolt which seems integral is curved so that makes sense. Any idea the size you ordered and length?