Up for sale here is this little plastic socket with screw from a Marantz 6300 turntable. This goes in the plinth and is used to hold a spare headshell (not included). It is in great condition with light wear, and will work great for you. Please see my pictures for details.
US shipping and handling is $5, and international is $18, no matter what quantity you buy. All my small parts are set up for combined shipping, so just use the "add to cart" feature and then check out all at once, and it will combine shipping. If you have any questions, please ask.
I have lots more Marantz 6300 parts listed--feel free to take a look! If it's not listed, I don't have it.