For most of the thousands of Americans who need a new kidney, there are only two ways to go: persuade a friend or relative to donate, or get on the transplant waiting list.

Yet some New Yorkers with the right connections and a pile of cash appear to have explored a third option.

"I have met many, many people who have told me in confidence that they have bought a kidney. Prominent New Yorkers. And it happens right here in America," said Robert Berman, founder and director of the Halachic Organ Donor Society.

Related: Israeli Man Sells Kidney to American Businessman for $20,000

Berman leads an organization that encourages Jews to become organ donors the legal way — without payment — but said he is often approached by people who need a kidney badly enough to consider paying for one.

Sometimes they even ask for his help finding a broker — a middleman who will arrange a transplant with a paid donor.

Experts and law enforcement authorities say a handful of these organ "matchmakers" based in Israel have recruited hundreds, maybe thousands, of people to voluntarily sell their kidneys to wealthy patients, including some Americans.

Much of their work has been done overseas, at hospitals in places like South Africa, Turkey and the Philippines, but experts say these brokers have arranged transplants in the U.S., too.

One of those syndicates plays a role in the tale told by Nick Rosen, a man who lives in Israel and made a video about donating a kidney to a Long Island man in 2005.

Rosen told The Associated Press he was paid $20,000 for the transplant in a sale handled by an organ broker in Israel who recruited him through a newspaper ad.

He said the middleman arranged for a series of tests to confirm his kidney was a match, then had him fly to the U.S. for an operation at a hospital in New York City. He videotaped some of his encounters with brokers, doctors and the man getting the kidney.

Paying for a kidney is illegal in the U.S., and Berman said when people ask him for help connecting with an organ broker, he always refuses. However, he supports legalizing certain financial incentives for organ donors and said he can't condemn the brokers for work that saves lives.

"I've met some brokers, and they are not evil people. They want to help other people and they want to be adequately compensated for running the risk of going to prison," he said.

The legal peril of getting involved in an international cash-for-kidney trade was highlighted in late July with the arrest of Brooklyn entrepreneur Levy Izhak Rosenbaum.

Federal prosecutors said Rosenbaum was caught in an FBI sting offering to arrange a kidney donation for $160,000. This one also allegedly involved a donor from Israel coming to the U.S. for a transplant.

Rosenbaum boasted, in a conversation recorded by the FBI, that he had been doing this kind of work as a "matchmaker" for 10 years and had brokered many successful transplants, including one just weeks before his arrest.

Berman declined to talk about Rosenbaum's case but said, "If people think he's the only person out there who was doing this, they're wrong." Rosenbaum has not entered a plea, and his lawyer declined comment after the arrest.

Indeed, while Rosenbaum's case apparently marked the first time someone has been accused of arranging transplants on U.S. soil, a number of similar operations have been broken up in hospitals where doctors asked fewer questions,

Some openly advertised in newspapers, seeking people willing to travel to give a kidney. Others even tried to strike deals with hospitals, guaranteeing a certain volume of transplant patients in exchange for access to operating rooms.

The crackdowns and recent changes in Israeli law have made it much harder for the brokers to stay in business, Scheper-Hughes said.

In the United States, she said, there are still people accepting cash to donate kidneys, but the transactions are more likely to have been organized privately between donors and recipients who connect through Web sites like Craigslist or MatchingDonors.com.

"Rosenbaum wasn't the tip of an iceberg, but the end of something," she said.

One thing hasn't changed: The need for donors. There are more than 100,000 people in the U.S. on waiting lists for an organ transplant, according to the United Network for Organ Sharing. Last year, 4,540 died waiting for a kidney.