I stumbled across this site: http://kodeks.uni-bamberg.de/KodeksE.html dedicated to Medevial Slavic Languages study. Among others, there are electronic texts of various manuscripts from 10th century onwards.
There is a message on the page saying: The material presented here may not be re-published without the written consent of the authors. All rights reserved.
Well, now I just need to get in contact with St. Constantinus and St. Methodius....