Up for sale here is this Marantz 6150 RCA cable set with ground wire and attached grommet and metal plate, plus the small circuit board. These are in fairly good shape but the RCA cable ends are a little discolored, though they may clean up with a good scrub. These are untested and will probably work fine, but they may need to be cut off at the grommet and shortened a little--this does happen with vintage turntable RCA cables sometimes. Please see my pictures for details.
US shipping and handling is $6, and international is $28. If you have any questions, please ask.
I have lots more Marantz 6150 parts listed--feel free to take a look! If it's not listed, I don't have it.