If you go to the HealthGrades site, I think you'll see 501(c)(3) hospitals listed as elective nonprofit or something similar. If you use the first two sites, you have to narrow down your search results with a component of the hospital name (since they list all nonprofits, not just hospitals).
It'd probably be more useful to have a listing of hospitals that are NOT 501(c)(3), since most non-government ones are nonprofit.