Start at Maryland Metrics, as already suggested.
Last time I looked, which was a long time ago, there wasn't a DIN standard for pan head screws, but there were standards for somewhat similar but not so tall 'cheese head' screws.
When the 'Merican car manufacturers started converting to metric, they did pretty much as they pleased, standardizing their own pan head screws with metric threads. ... which they could do, because they buy so many of them.
Mike Halloran
Pembroke Pines, FL, USA