Yes, it is possible. What you are describing is usually called an anti-sleeping bench or a bench with a center armrest. These benches are available from outdoor furniture suppliers, and many cities already use them in public spaces.
If you are buying new, look for terms like “center armrest bench,” “anti-sleeping bench,” “hostile architecture bench,” or “bench with dividing armrest.” Commercial site furniture brands and local metal fabricators can build one to your specifications. You can often choose the armrest material, finish, and position.
If you already have a bench, you can retrofit it. A metal shop can weld or bolt a center armrest onto the seat or frame. Powder-coated steel or aluminum is common because it holds up outdoors. The armrest should be sturdy, with rounded edges, and placed so it divides the bench into two shorter sitting areas. That makes it uncomfortable or impossible to lie flat across the whole bench.
A few things to keep in mind. These benches fall under what some people call hostile architecture or defensive design. They can be controversial because they target people who have nowhere else to sleep. Before installing one, check local regulations, public space guidelines, and accessibility requirements. Some places discourage or restrict designs that intentionally prevent sleeping.
If you want a less obvious option, consider a bench with individual seats, a sloped seat surface, multiple armrests, or a planter in the middle. Those can achieve a similar result without looking as aggressive.
So yes—you can absolutely get or make one. Just search for “center armrest bench” or ask a local metal fabricator, and be prepared for the practical and ethical questions that come with it.