I've got a Vino, not too sure about the metro's cockpit, but we simply have a clamping system that should hold onto a standard set of motorcycle bars.
In general, motorcycle handlebars are 7/8" tubing, so any standard motorcycle handlebars SHOULD work if you find a set you like. Scooters should be no exception to this rule.
edit - the bars are a 'cafe racer' style, like these ones on eBay. I'd just like to see exactly how they look from a few other angles, as I'm considering a set of some kind on my vino.
ebay auction:
http://cgi.ebay.com/ebaymotors/ws/eBayI ... MEWAX%3AIT