Seeking Feedback on Research Topic Outside Department/University
I too had a topic which was outside of the expertise of my committee. If you are set on your topic, this seems like a good approach. After talking to your current committee and getting their buy-in on the plan, you could also approach other faculty at your current institution to tap their networks.

Another way of doing some networking to get feedback is to attend local or subject area conferences. The big AEA conference is pretty difficult to use for networking, but you could make contacts at these other conferences which could be helpful. Especially once you get your work to a poster stage.

I would also like to advocate a second idea, which is to change topics to something more similar to your committee's area of expertise. While this is not what I did, I definitely saw the merits of it as my friends who took this approach were able to coauthor with their committee, have more useful RA experiences, and come out with more lines on their CV for the job market.