When most agents hear the word "assignment" they tend to not be interested. Short sales, foreclosures, and most resales will not deal with an assigment - it's just has too much potential for failure.
Agents only get paid if the transaction closes escrow. Why would they want to get involved if there is not a good chance of success?
There is an Internet based company called Zip Realty. Once a person registers with Zip they have access to MLS listings in most markets. You will be assigned an agent and this agent can do research, write offers, negotiate offers, etc. for you. Most of this can be done via e-mail. Zip gets a data dump from the local MLS's about every four hours. A client cannot see the confidential remarks to agents (how to get into the house and other comments relating to offers, etc.) but they can see almost everything else - address, time on market, etc. If you require more information, send me an e-mail.