What I meant my a USB to AUX ditto is that some of those USB to FM transmitters also has an AUX out. Here are some examples at Amazon:
https
/amzn.to/2J56jl7
Going back to that you said you currently use an iPod in the other car and would like to do the same in this one, there are also similar-ish solutions with an iPod dock instead of a USB port, if you replace the USB part in the search with iPod dock.