Good point. So what was it that gives that lovely super-shallow depth of field and that difficult-to-describe bokeh?
It was long focal length lenses, and undercorrected lenses that gave the look you are wanting. Longish, portrait-style lenses may be what you are looking for, but don't expect ultra-fast lenses. Back in the 19th century, people just had to remain still for a few seconds when they had their picture taken.