I also get a lot of questions about our vessel sink drains...where do I get them?? I purchase the decorative ones from sinksfaucetsandmore.com, and the more standard ones from Kohler (ferguson), Home Depot and Lowes. You'll want to make sure to get a drain for a vessel sink with no overflow (for use with our sinks).
Here are some of the more popular decorative vessel sink drains I've used from sinksfaucetsandmore.com: