Unless this individual can stand up to a healthy amount of due diligence from you (who are you? who is your firm? why should I have anything to do with you? etc.), I wouldn't even consider doing business with a cold caller.
If you have an account with any major discount brokerage (Fidelity, Schwab, etc.), you can call their bond departments and get shown a wide array of individual bonds to purchase. But make sure youare capable of doing sufficient research on the issers to avoid buying something that should not be rated what it is. Lots of people have lost lots of money buying highly rated bonds that they knew nothing more about than the rating and the issuer's name.
"There are three kinds of men. The one that learns by reading. The few who learn by observation. The rest have to pee on the electric fence for themselves."
- Will Rogers