RE: Hot Pretzels on Hot Dog Cart, like NY style
New York Pretzel Co. supplies the unbaked pretzels to the pushcarts in the greater NY area. I'm sure they'll ship.
The key to a real NY pretzel is to use charcoal to heat them up. Most of the pushcarts have a "hole" in them that holds a couple of pounds of lump or briquettes. Over this goes a screen basket with the pretzels in it. You need to have the coals to give the pretzels that crusty, slightly black charring - kind of like a coal oven does for pizza.
There are a couple of other pretzel bakeries in the area (Kings Bay Pretzel, and one whose name escapes me) that also supply the bake off items. I've used both NY and Kings Bay for events that I've run, and their product is very good.