I hate to sound critical, but what use is excellent rear visibility if you cannot turn your head enough to use it?
The solution is clear enough. If you cannot use your direct vision then you must rely more heavily on your mirrors. And if that is still not good enough, you must exercise extreme caution in changing lanes, double- and triple-checking.
But let us help you find a car. Nearly all sedans offer excellent visibility to the rear and to the sides. The few exceptions, such as the Dodge Magnum, are well known. Get yourself a copy of Consumer Reports' New Car Guide. This publication reviews all models and it emphatically points out those that have restricted rear/side visibility. If CR doesn't complain you can be sure the car has suitable visibility.