Are you looking to see grizzly bears or black bears? Are you open to going at any time and anywhere in Alaska? Seems like you might need to narrow down your options a bit. Most bear viewing requires a fly-in. But you can see bears in Denali NP (grizzly bears) all summer with patience and time.

Any fly-ins will be relatively expensive (figure $600+ per person for a day trip, more for overnight). I would never book a day trip fly-in to see bears.

I would say there are a lot more than 3-4 "hot spots" for bears. Off the top of my head I can think of Anan Creek, Pack Creek, Katmai NP (multiple locations within the park), Lake Clark National Park, Denali NP, and Kodiak Natl Wildlife Refuge.