There may be some out there, but you probably don't want them if you really want to sell your house. ;o)
I know 2 -3% or more sounds like alot of money, but you have to realize the Realtor is paying for all the marketing out of their own pocket, splitting the fee with their broker, plus paying income taxes. So at 1% commission on a $500,000 house, the agent is really only left with $1500 to cover marketing expenses and their time (often over 100 hours). Virtual tours can cost $500 alone, not to mention up to $100/week for newspaper ads. At discounted rates, you will not be getting a full marketing plan - and in this market homes that are just put in the MLS aren't selling.
Your best option is to find one agent to act as both your buyers agent for your new home and listing agent for your current home. Then the agent is more likely to offer a discount on the listing, as they can subsidize it on the purchase.