Dear pita,
I started the other thread. I have now found all the info on this, and plan to do it next spring here with our chamber orchestra. Here you are:
There are no published scores of this! The manuscripts for the piano score (which has Beethoven's own embellishments) are held in Vienna, and the string manuscripts (arranged by a contemporary of Beethoven) are in Bonn, Germany.
Dr. Hans-Werner Kuethen in Bonn put these scores together and postulated they were meant to be played together. He wrote a research article on this, published in the "Beethoven Newsletter (Journal)," vol 13. He has the rights to the combined score. By contacting him, you can get a copy of the scores, and it is 150 Euros. You also have to send a signed form stipulating that you will announce the performance, give Dr. Kuethen the proper credits and follow the procedures he requests.
I am awaiting the scores now. Dr. Kuethen was very accomodating in his emails. If you want to contact him, let me know--PM me, and I'll give you the contact info.
Robert Levin recorded this on period instruments.
All the best,
Teresa