I've actually been doing a lot of searches myself for this type of property recently; unfortunately, none of them met the very specific requirements of the buyer I was researching for.
If you're still looking, I have some interesting leads in all four boroughs and would be happy to put together a list for you. Obviously, the seller pays for the marketing/sale of his or her property, so using the services of a real estate agent is free for you (and even if it weren't my day job, I would strongly recommend that any buyer use an agent, if only for the time-saving free labor and negotiating!)
Feel free to send me a message if you need help. I can turn around a search for you in a matter of a few hours--and not just my company's listings, but a comprehensive picture of what's out there.
Douglas Elliman Real Estate
Please call for more information.
Licensed Real Estate Professional
If I can be of help or you have further questions, please give me a call, 917-335-8569.
Best of luck!