Glad you found an NB and nice meeting you at TMS a few weekends back. There's a good Miata salvage yard in Kennedale (long haul from Frisco), but they typically have first gen Miata's. Second gen's are out there, but harder to come by from what I've seen.
Try parts searching using www.urgntx.com and then call before you go.
EDIT - Mazda-Nissan Heaven is the place in Kennedale