CVS and I'm sure others make single use disposable units for $2.80 for four of them. I'm fairly certain if you search you can find them in bulk, one of the people I know who uses them mentioned she buys them in bulk when she travels for her daily injections
http://www.cvs.com/CVSApp/cvs/gatewa...?prodid=420997
If by any chance he's in New York State on his travels, their full listing of collection sites is here
http://www.health.state.ny.us/diseas....htm#directory
I don't know if other states maintain such a listing or not.
By law in NY, all hospitals and nursing homes have to accept sharps from the public.