Pretty much any EM residency offers a "sub-i" in EM, whether they title it as such or not. Places that come to mind: Denver, LA county, Indianapolis, BIDMC, MGH/BWH, NY Presbyterian, Christiana in Delaware, Georgetown, SUNY Downstate, UCLA Harbor, SUNY Buffalo, Cincinnati, and I could go on for days.
Like I said - pretty much any EM residency will offer one through their affiliated medical school.