Any Machaca in Raleigh area?
There was a thread on this about a year ago, but I can't find it. IIRC, someone said that Las Cuatas on Capital in Raleigh has it. Fonda y Birrieria Jalisco might be a good bet also, as they have regional specialties from all over Mexico.
If you're desperate for a fix and have no alternative, El Sol in Mount Olive was advertising it a month or so ago.