wow they are sold out.. never would have guessed it but they have awesome products. this is the one I used, but any other brand with the same ends will work

Audi Stereo Fakra Female to ISO Female Antenna Adapter Cable https://www.amazon.com/dp/B01M0WUIDJ/ref=cm_sw_r_cp_apa_i_j-q2BbMF0A7TM