So in favor of practicality, if you're looking for simple and easy then go with the pickle (did you know they even sell prepackaged pickle-in-a-bag? Probably very not cost-effective though), a bagel (can you even get bialys anymore?) and a small bottle of seltzer, and then focus on the packaging. The other ideas are either more complicated and/or more expensive.
new york cheese cake is considered a jewish food that originated in new york - supposedly the inventor of reuben and rachel sandwiches invented cream-cheese cheesecake;
1929 – Arnold Reuben, owner of the legendary Turf Restaurant at 49th and Broadway in New York City, claimed that his family developed the first cream-cheese cake recipe. Other bakeries relied on cottage cheese. According to legend, he was served a cheese pie in a private home, and he fell in love with the dessert. Using his hostess recipe and a pie she made with ingredients he provided, he then began to develop his own recipe for the perfect cheesecake. Reuben soon began to serve his new recipe in his Turf Restaurant, and the cheesecake quickly became very popular with the people who frequented Reubens Broadway restaurant
As for kugel - any east-european jewish food can be pulled of for a LES theme, its easier to make the knishes
If people will need Google to figure out the reference, it doesn't count.
And disagree that LES = Eastern European food. LES was the world's biggest melting pot from all places, plus it's not a LES theme if you're going with Eastern European. Knishes have LES association because they were a classic pushcart food. Kind of the equivalent of today's stands with hot pretzels and roasted nuts. And LES was the pushcart capital of the world. You can eat a knish with your hands while standing on the street if you have to.