The Banks turbo has what is known as a T4 flange - that's the flange pattern at the exhaust interface.
There are many other turbos out there with T4 turbine inlets, so there are plenty that would physically fit on the exhaust manifold. You can also get adapters to fit turbos with other patterns on there (like a T3 to T4 adapter).
Now, while you could physically bolt on a lot of different turbos, that doesn't mean that just grabbing any old one that fits would be a good idea. You'd want to match it to your engine, intercool it if necessary, not get too much boost, not get too little airflow, etc.