I've had excellent success with this one:
https://www.amazon.com/gp/product/B0BNMKS29M/ref=ox_sc_act_title_1?smid=ADX9QPJT7HI2R&th=1
There's a thread about my experience with it.
Looks like the automotive version of the Stadium Pal. If you've never heard the David Sedaris story about the device, do give it a listen. Great stuff indeed!
Check my fairly recent thread for my roadtrip mileage experience.
https://www.mavericktruckclub.com/forum/threads/just-back-from-16-day-4500-mile-trip.82859/
But they did have that great "shelf" in the rear window for us kids to ride on (remember the quarrels with your siblings/friends about who's turn it was???).
You've clearly been spying on me. I do exactly the same. I will say that here in Philly, we have one of those super-powerful AM stations, KYW Newsradio, and the signal is crystal clear (I'm sure it's the station and not the Stubby Jr.!).