I assume you bought the bike 2nd hand? So didn't fit it yourself?
Also we don't know your location!
Easiest way/generic answer would be to find a bunch or motorcycle taxi guys sitting on a corner and ask them. They will take you for a fee to an accessory shop.
Need more specific answer? We need a location!
Where can I get a PROJECTOR H4 DUAL XENON globe to replace the failed one in my HONDA CB300F?