Try Metro Parent Relief. They do exactly what you need.

We are likely moving to the DC suburbs (not sure if it will be northern VA or MD yet) and I am wondering about whether there are any good nanny services available. I will need someone to take care of my 1-year old for 3 days/week (Mon, Wed, Thur) during the summer. Does anyone know of a good nanny service? I am looking for a service that will send a new nanny if someone is not good or does not show up to work. Since we're moving on short notice, I am assuming I won't be able to get my son into daycare that quickly... Thanks for any help!