I had the same problem on my "D" shaped wheel. Wheelskins makes a custom leather cover for the "D" flat bottom wheel for $ 69.00.I installed a cheap one on my 2018.
Easy on. However the "D" section on the bottom of the wheel causes the cover to "slip" and not stay centered. I then installed two plastic wire ties to pull up the cover in the "D" section. Works great.
When I first installed, I WRONGLY thought that it would affect the "keep ha dad on Steering wheel" message. Yes, the message still can come up, but after learning on this forum, it's not holding g the steering wheel that causes the message to disappear, it is steering wheel MOVEMENT that causes the message to disappear.