Do a search for "Bluetooth media remote control" wherever you like to shop. You pair such a device with your phone (not the car). For the lazy, I found this one on Amazon for $13.99 (actually, $16.99, but there's a $3 coupon that applies at checkout): https://smile.amazon.com/Wireless-Bluetooth-Control-Motorcycle-Steering/dp/B081RLWSTL (this one even comes with a handy little ring mount to clip it to your steering wheel or handlebars on a bike, or you can just use a heavy-duty temperature resistant double-sided adhesive strip to stick it wherever you want it).
One of these will work just fine. Just pair it to your head unit via bt.
Ps. This is just an example, i have no actual experience with this particular brand. You can find many others.