At clinicaltrials.gov, this is contained in the main record if the trial is still recruiting, and in the archive if not. At ISRCTN it doesn't seem to be listed, but a contact person and their institution are given. Might be worth seeing how many institutions are covered and whether it's possible/worthwhile to infer email address format for each one. An alternative would be some kind of crordsourcing interface a la the election candidate info. duck house game http://www.democracyclub.org.uk/blog/2010/03/play-our-new-game-win-a-duck-house/