May I suggest another, probably much cheaper suggestion, and that is taking your car to a top rated upholstery shop? The good ones are masters at literally taking a piece of extra-firm seat foam, sculpting it in a precision manner, inserting and attaching it underneath your factor upholstery (whether it is vinyl, leatherette or leather), then re-installing the OEM covering.
I have a friend who had back pain, even on one hour trips. He took his Corvette into a local upholstery shop, had the above lumbar addition done for both his and his wife's seats for about $125 total, in about 1 1/2 hours, and they now take long trips without issue.
Here is how the process was done on a motorcycle seat, though this was "foam subtraction" not addition. Note please that there are many different grades and foam density options, though a good upholstery shop will probably already have, and if not can get you what is needed for your lumbar support.
One additional note, is that each of us are build different, have different amounts of "fleshiness" or lack there of (duh), and my daughter and her husband take long trips in their 2016 Mazda 3 and love their OEM seats, do not want anything changed.