If you are set on the Master's, I'd ask the program directly where and how students with scholarships get funded, for ideas of where you can apply for $. Some people must have funding, so I assume maybe there are some opportunities you can try for, at least in the second year...and I think NYU matches aid you pull in, if I understand it correctly.
You can also try reaching out to academic departments that have high undergrad enrollment but few PhD students -- they sometimes need to expand their teaching workforce and so offer TAships to master's students. But this is not an opportunity available everywhere, not sure how common it is at NYU.
If you think you could stay at NYU for the PhD and it's aligned with the master's, you could also try reapplying to the PhD this year (after starting the master's). In engineering disciplines at least, it's common for the first 2 years of PhD to overlap pretty heavily with the Master's coursework (+quals of course), and if the professors are the same solid letters of rec from them could really give you a strong application.