Why should private companies open up their accounts to some shitheap self-appointed defenders of democracy? It reminds me of those dicks from 38 Degrees.
Info here: http://whofundsyou.org/
General finding is that right wing think tanks are more secretive. That may well just be because they get their money from private donors rather than the taxpayer - so of course there's a duty on one to be open and the other to protect private information.