Unbalanced to balanced adaptor

I'd like to take advantage of the AES/EBU digital input DAC -- just for the additional input. It's a balanced input, but none of my sources is balanced, and the unbalanced inputs of my DAC are already used. Are there cable adaptors that will allow me to take the S/PDIF (RCA coax) output of a transport into the AES/EBU (XLR balanced) input of my DAC?