Good attitude. Tricky goal.
Well you can always grab the links from my "from the mouth of the users." Not specific to your situation but will give them some ideas of the difficulties people have.
Pointing to Texas and the fact that future court cases are more expensive then doing it right. Pocket Books speak really loud.
Examples... would you mark documents with a color code if you knew the employee using it was colorblind? My former boss was, so always had issues with people using red to highlight things as he could not see red.
then there is my old standby, what about next year? Do they want to re-do something in a year because they hire a new employee who has an issue? Do they want to re-program something because a current employee looses some of their ability due to an accident, illness etc.? No one knows what tomorrow will bring, how often do they wish to rework it and how much would that cost? Transferring a person or letting them go would be legally questionable and quite expensive compared to thinking ahead and doing it right.
I guess what I mean is people rarely do what is right for the right reasons... So like food designers who use white glue on ceriel so it looks pretty in photos, we must convince them it is better to do it and the pocketbook is the best way. It is our dilemma when doing the right thing is not enough.
Good luck with it.