Honestly, I get this question a lot from property managers and city maintenance crews. The short answer is: it depends entirely on the manufacturer and the specific model, but in most cases, yes — you can order just the backrest, especially if the bench is from a commercial or municipal line that still has spare parts available.
Most reputable urban furniture brands — think Maglin, Landscape Forms, Streetlife, or Benchmark — design their benches in modular ways. The backrest is usually a separate component bolted onto the seat or side frames. Because these benches take a beating outdoors and get vandalized or damaged in accidents, these companies know that replacing an entire bench for one broken slat or bent backrest would be ridiculous. So they typically keep a parts catalog. You need the exact model number, which is often stamped on a small metal tag under the seat or on one of the legs. If you can't find a tag, a photo sent to the manufacturer's customer service team usually helps them identify the model within a day or two.
However, there are a few caveats. If the bench is older than, say, 10 to 15 years, the manufacturer may have discontinued that model and no longer stock the backrest. In that case, your options are to get a custom metal shop to fabricate a matching backrest, or to order a complete new bench — which stings, but sometimes it's cheaper than a one-off custom part. Also, some budget-friendly or big-box store benches are sold as non-serviceable units, meaning no individual parts are available. You didn't specify the model, so if you can reply with a photo or the brand name and any numbers you see, I can point you in a much more concrete direction.
Another practical tip: even if the manufacturer doesn't sell directly to the public, they will almost always sell through a local dealer or distributor. So don't be surprised if they say "contact your regional rep." That's normal. Ask for the part number and price, and ask whether the backrest includes mounting hardware or if you need to order bolts separately. Some companies ship the backrest bare metal, others pre-finished. If you're replacing because of rust or damage, consider ordering the upgraded coating or asking for a marine-grade finish if it's near salt water.
In short: yes, it's very possible to order just the backrest for a specific urban bench model, but you need the model info and a bit of patience with the manufacturer. If you share the brand or a photo, I can help you find the right contact or part number.