Welcome to the forum.
First of all have you tested your battery, how old is it etc.
There are several threads on how to test the regulator and a plug to test on here. If i run across it ill post it up here.
As for replacements ricks motorsports is a good choice or I think americansportbikes carries OEM style.
There is a link to the service manuals at the top of this page it has all the testing procedures in it. That'd be a good place to start.