Just to add to anyone reading this post for informational purposes, so long after it was posted by the buyer...who hopefully has purchased a home by now.
I dont see where anyone mentioned that the listing agreement the Seller has with their listing agent is for the full commission, whatever amount that is. Then,the listing agreement may have condiitions about what part of the commission will be offered to the buyers agent. It almost never specifies an amount of commission to go to a buyer without representation. So a buyer without representation would not cause the terms of the commission to change to the listing agent.
Further, most listing agents would feel that their work to market the property attracted the buyer to the property, rather than the buyer being brought to the property by a buyers agent. After all, a buyer would not know about the property if it was not marketed. Most Realtors who list homes have had the experience of representing both the buyer and seller in a single transaction. In fact the first page that a buyer or seller should sign with a Realtor in California discloses the "expectation" of representation of the Realtor to the buyer, the seller or to both.
Another item for consideration is that Realtors act within the contraints of their brokerage. Most brokerages have a minumum that a Realtor can accept to work with any party, buyer or seller. So, asking for 3% back or off and representing yourself may not be something that the Realtor is authorized to do.
Perhaps you should contact the Realtor representing the property and ask them to represent you and write your offer and mention up front your request to be rebated part of the commission. This will allow them to know up front what the expectation you have is in working with them. Depending on the purchase price and type of transaction, it may or may not be a prudent business choice for that Realtor to elect to give you a rebate and in that case you could look for someone more appropriate for your real estate needs.
There is someone for everyone when you are hiring a professional. Remember too, sometimes you get what you pay for.