2 paved pump tracks are not necessary close but vernon nj and port jervis ny . Dirt pump track in west milford nj that may close at a certain time of year . Nyack has a small concrete skate park that might be fun . Cunningham in queens has a few options for pump tracks and jump lines as well . On crappy weather days sometimes a vacant parking garage can provide a perfect spot to practice manuals and bunny hops .
Having a kid that races BMX, I'm relatively in tune with what's around. Here are the Paved Pump tracks I know of that are in, or are close to NJ, with a bit of info on each.
Port Jervis Pump Track: Pretty big and fast and the layout allows for some creative lines, but the basic counter clockwise outer loop itself is quite good.
Vernon Pump Track: Med size, tighter and smaller than Port Jervis. Nice design
Camp Olympic (Emmaus PA): Med size. Kind of a cross between the above two. Part of a bigger park with a playground so can get crowded with little ones
Neptune Skate Park: Small concrete pump track line. I've never been
Penn forest Pump Track (Jim Thorpe PA): I've never been
Philly Pump Track: Small tight asphalt track and a smallish dirt BMX Line. Only open certain days/hours
My opinion is paved pump tracks are A LOT more fun than dirt tracks. Also, If you spring for an annual USABMX License, you can ride Practice at most BMX tracks on practice days and/or practice sessions before races. Price varies, but Hunterdon charges $5 for practice. I do this ALL the time at small local races while my kid is racing. The Hunterdon track actually runs downhill, and isn't super tight and it's a blast on a DJ IMO. Turns are asphalt and the dirt is "glued" so it's smooth and fast.