How can I find a digital forensics expert to help trace stolen bitcoins? Are there any professional organizations that have lists of blockchain analysis and digital forensics experts by location?

I know some of this work can be done online but a directory of experts by location would be helpful, since I prefer to work with someone locally.
I'm not sure of the existence of a directory of experts by physical location since Bitcoin is a digital currency.

Elliptic is a blockchain intelligence company identifying illicit activity on the Bitcoin blockchain and providing services to leading Bitcoin companies and law enforcement agencies globally. Their HQ is in London and main office in New York. More information of the company is available here. If you're based in either of these locations you could contact them locally.