Jackson Heights Life

I live in a co-op here in Jackson Heights. My toilet is the flushometer kind (Zurn Aquaflush WS1 LC) and needs to have its diaphragm replaced. The co-op manager knows no one who can do the repair. The super is retiring soon and no longer does these kinds of jobs. The manager told me to look for a plumber with a COI (certificate of insurance) and a license, which he will have to verify, so I need to coordinate the repair with him. Does anyone here know any qualified plumber who can do this kind of job? My super did this job many years ago and it took him about 20 minutes to replace the diaphragm, but we're living in a different world now. Thank you in advance for your assistance.