Try some of these search terms, along with the name of your state:
Sharps disposal
Disposal of sharps
Needle disposal
Syringe disposal
Or try your city's/county's waste management site.
When I was at my local pharmacy, I asked where to take my sharps containers, and the pharmacist gave me a printed list of facilities that accept sharps. My GP also gave me a flier put out by county services, but I misplaced the flier. Duh.