Robin:  We use two firms for U.S. derivatives advice - both in New York and both  highly recommended:  David Mitchell of Cadwalader, Wickersham & Taft (212)504-6285 Ken Raisler of Sullivan & Cromwell (212)558-4675  David we use for contract issues - what should our forms look like under  various conditions, etc.
and Ken, who is a former General Counsel of the  CFTC, we use for policy questions, political (lobbying) and e-commerce  issues.
Please feel free to use my name when contacting either of them.
If  neither of these is exactly what you are looking for, let me know and I can  put you in touch with others.
Mark

Derivatives Counsel