Buy a Data Basic with AES/EBU output from the classifieds. Move over the wiring and the connector (basic soldering skills needed) to your Data Basic, and resell the other one.
In any case, I can sell you a nonworking Data Basic I (transport mechanism failed) which has been upgraded to mk II status for parts needed to perform the upgrade. The only difference between Basic I and mk II, is an extra transformer in the later, which need to be moved over.