Well,, a couple of ideas here, if they help ...
First of all, re: lawyers, did you try contacting the obesity law lawyer in San Diego, Walter Lindstrom? He has pretty good success at getting arpproval, so long as there is not a blanket exclusion for weight loss treatment in your policy (those are pretty insurmountable) .. It sounds like you don't have the blanket exlcusion situation, though .. There is another obesity lawyer (I think he's in NY?) .. can't remember his name, but he supposedly has a lot of success for his clients, too ..
Secondly, hasn't your surgeon's office helped to get you approved? I think most of them these days have a full-time staff member (or even more than one) who has that as their primary (or only) job .. It's an evil necessity of the profession, and knowing how ins. cos are increasingly bogging down the approval system .
Another thing to consider is getting a cash loan to pay for the surgery, using one of those services (I know of one gal that put hers on a credit card after getting her credit limit increased!) .. You could then take your time making your ins. co. reimbuse you for the cost later, so you can pay off the loan, once you prove up "medical necessity" to them ...
Lastly, I know of a gal (a former client and close friend, too - who weighed 500+ lbs.) who got her VBG approved from Blue Cross of Texas only after she "faxrassed" them .. She simply faxed them copies of ALL of her medical records until they approved her .. We're talking stacks and stacks of paperwork, several inches thick .. They couldn't shut off their fax b/c of other customers/insureds that needed to fax them things, so it was either have her tie up their fax machine or approve her - and they did! (pretty sneaky, but I don't know if it would work today with caller ID stuff - but then I guess you could fax them from different phone #s to get around the block!) &;-)
Best of luck to you and please let us know how it goes ..