Here is a link to the (signal) contacts for the docking connector, five of which are required to add the tuner connector:
https://www.digikey.ca/en/products/detail/hirose-electric-co-ltd/QR-P1-PC2A-111-12/465897 (order five, plus some spares).

There are also some larger (power) versions of those, for the Power/GND connections of the empeg, but those are already installed and you don't need those: https://www.digikey.ca/en/products/detail/hirose-electric-co-ltd/QR-P1-PC1A-111-12/465895

If you want to leave the existing connector alone and instead wire up a new one from scratch, then order sufficient quantity of both kinds of pins, along with one or more of the actual docking connector shell: https://www.digikey.ca/en/products/detail/hirose-electric-co-ltd/QR-P6-24P-C-01/465919[u][/u]