I'm sorry your not getting any answers. The truth is most gardening furniture stores have been cutting back or going out of business. The big box stores are so much cheaper. BJ's, Costco, Home Depot, Lowes, etc. Even Home Goods gets stuff in but their season is winter after Christmas believe it or not.
What exactly are you looking for?
If it's tables, chairs and umbrellas or sofa sets, there is Fortunoff in Wayne. Now that it is August, they will be cutting back on display space and putting up Xmas but everything should be on sale. That is the largest, most consistant I can think of. Also there is Fountains of Wayne, also in Wayne on 46 W, just before the intersection of 80, 23 and 46. They are close to each other. I don't like them as much.
I'm sure Bergen County has a few spots on or near Rte 17 and Rte 4. Maybe someone can elaborate.
Otherwise, there are smaller places that have more specialized offerings. On Rte 23 in Riverdale, there is a little florist shop next to Circle Farm. They carry organically carved wood pieces and petrified wood. Pieces run in the hundreds to a few thousand. You would never know it's there. Many nurseries offer some kind of limited choice including bistro sets, arbors and trellises, wooden table sets, fountains...

Well, in the Paramus area, most have gone out of business (Harrow's, Treasure Island), but there is a Fortunoff Outdoor Living on Rt. 17 North in Paramus, a little bit past Rt. 4. I've never been there, so I can't give any opinions on their stock or prices. There's a Ski Barn Outdoor Shop, also on Rt. 17 North, but if it's anything like the ski store, it'll be ridiculously overpriced. I know Home Depot is having a 50% off on outdoor furniture. They actually had a nice little set I like, and I never like their furniture. I'd hardly call it a large selection though, and I haven't a clue as to how "large" the selections are at Fortunoff Outdoor or Ski Barn Outdoor.

We recently purchased a firepit and 4 upholstered chairs from Costco and found a large brown square table with seating for 8 at Pelican on Rte 10 West in Denville. They have a website.

the garden cottage on the Country Mile in Harding has very nice patio furniture and all sorts of stone benches, fountains and the like. They can order almost anything for you.

I wish this post was up a few years ago when i lived in NJ. Patio dining sets were hard to come by for me.