Another one to recommend doing Churchill independently in summer. You can rent a hotel and a car independently for a fraction of the cost of these tours. Mind you, in any case getting to and from Churchill is expensive. Several pods of Belugas are present in the estuary all the time. You can snorkel with them if you want to. They are curious and swim on their backs looking at you.
Unlike Jos I rented a car. I birded on foot in a patch of dense shrubby forest, and was really scared when later a huge male polar bear emerged from the same forest. So the polar bears can really be anywhere. I saw a Yellow Rail (under aurora borealis), Snowy Owl and Harlequins. Very nice tundra-boreal forest birding.
Had an interesting thought about that Yellow Rail. First thought: wow, I just saw a Yellow Rail under aurora borealis. Second thought: I am just standing in a freezing swamp water at 1. a.m.