We are located in Long Island, New York. While we are happy with our current programmer, we are looking for a programmer to pick up the overflow work. Ideally we would like someone to be able to work onsite. Willing to pay a good hourly rate...depending on ability.
For short-term assignments where physical proximity (e.g. lives in Long Island) is a necessity, a good temporary employment agency that specializes in professional employees is a good option. The skills you are looking for are relatively easy to find, but an agent can be worth his/her weight in gold on both sides of the hiring process. "Time is money."
Incidentally, your present programmer might be able to drop a few recommends!