Hi Kathy,
At present, there's not much available for the 1/72 U-boat that doesn't already come out of the UK or EU.
Nautilus Models is supposed to be releasing some conversion sets for this kit, but there's no timeframe yet that I'm aware of.
Sadly, there's not much in NYC anymore either...there Jan's Hobbys uptown, but it's *ahem* pricey to say the least.
Your best bets for hobby shops will be the following...
Hobby Heaven in Cranford, NJ
Avenel Hobbies in Avenel, NJ
Ridgefield Hobbies in Ridgefield Park, NJ
These are all within 45 minutes to an hour from Manhattan.
Drop me an email, I work just outside the city at the NJ Aviation Hall of Fame and Museum, I can point you in the right direction once you're stateside.
Jeff Herne
Modelwarships.com
PS: Tell Nick to look at my Amati 1/72 Type VII conversion on Modelwarships.com, in the Features Section.