I assume 47mm is the diameter, plus you don't state material thickness, for example say 3mm al/al sheet will be ok, pay a visit (if possible) to a local fabrication shop, they may be able to punch them out @ the size your looking for, failing this, 50mm will be fairly standard punch, you can possibly dress to size??
Cheers....
Oops, I misread the post, been a long day wi laddies