Thanks everyone for the information. Unfortunately, it looks like I'm out of luck with Stan for the year. He says he had an unusually high number of people purchasing from him due to more people being at home on lockdown and taking an interest in gardening.
People are surprised to hear how mild our winters here are in NYC relative to the rest of the NE, but we have an urban heat island effect here coupled with being right on the coast that gives us a nice microclimate. In fact, if you visit certain neighborhoods in Brooklyn or the Bronx, you'll see many large fig trees growing unprotected that were brought by immigrants many years ago. We also actually lie only at 40 degrees latitude, which is further south than parts of NoCal and cities like Rome or Barcelona, though they have much warmer winters. Drive 45 mins out of the city though into rural parts of New Jersey and it's significantly colder during winter.
https://planthardiness.ars.usda.gov/PHZMWeb/From what you guys have suggested, I think a Dunstan Citrumelo and US-852 would be the best choices. Is there anywhere these are available to purchase or trade? I haven't been able to find a source for either.
Thanks again!