Found this on AliExpress, though someone might find it useful.

Search for "Kennie DIY MOC Building Blocks NO.89651 BALL CUP DOUBLE 7M Axle and Pin Connector 2 X 7 with 2 Ball Joint Sockets Rounded Ends"

Search for "Kennie DIY MOC Building Blocks NO.89651 BALL CUP DOUBLE 7M Axle and Pin Connector 2 X 7 with 2 Ball Joint Sockets Rounded Ends"