How do you buy your crops back on paper?

Lets say I haul 100 bushels of soybeans to the elevator.  The price on the board is 8.75 the elevator is offering 8.60.  I am given 2 options by the elevator.  I can either sell for 8.60 or I can put them on DP for 0.20  til Jan 1st.  I usually go with DP.  If I sold them how do I buy them back on paper?  Do I do this through the elevator or do I need to call some sort of broker?  What will it cost me to buy them back on paper? hopefully less than 0.20.  Sorry for asking such basic questions.