Oh, man. I was hoping you'd have something by now.
You know, this may be completely impossible, but when DH had shingles last winter, his doctor offered a shot in the shoulder that he said would numb the nerve all the way down the arm for a short while. I wonder whether something like that is available and might be safe in pregnancy because it's just a local anesthetic.
Wish there were more we could do. How long is your sister going to stay?