Ann Wagner would be a good replacement but she is set where she is. She is a lock-in for his old Congressional District, a sure thing that she will win without a fight. She would not trade that for this and I don't think anyone could blame her.
I have listened to discussions about viable replacement candidates and it is hard to come up with one especially at this late date.
This am one of our local media outlets had a professional Republican adviser discussing the 'state of the state of Akin'. (I am most certainly paraphrasing) Akin, Wagner, and Emerson are all good friends, and the belief was that should Akin bow out, either of these two ladies would be the 'best' candidate to take on Claire... for all the reasons cause by Akin.