These are great ideas, thank you! I do have some ethnic markets around me that would probably have better stuff than the chain grocery stores.It's not the easiest thing to do but if you can work up the courage to ask your neighbors, do it. My neighbors down the street have a wild grape that grows massively. They don't do anything to it and they are delighted to have me take some leaves.
It's probably the same for many hibiscus owners; they are so hardy (at least where I live) there isn't much need to use pesticides.
Since you're in a big city, you may have some other options near you in ethnic grocery stores. Do you have any hispanic, Asian or Persian markets nearby? Other cultures eat things we consider weeds.