First of all, a large bear is like three adult male lions in weight; or half of a medium sized car, if you prefer. Combine 7 furious heavy-weight MMA cage fighters into 1 person with killer teeth and large sharp claws and you'll start to get the picture.
So, most of these recommendations are even more of a fantasy than the already far-fetched idea behind it all. You won't be able to defend yourself against a bear with a knife, but I can understand your question though, because I wouldn't wanna die without a fight, even though I'd lose without question. All I'm saying is that after I died, I'd like it if people could say that the bear was found bled out under tree or at least limping on three legs a few hours later or something.
So, a Junglas, Busse, machete or whatever won't do the trick, because their blades are too wide with too much belly. You need something like a tanto, like mentioned before, or ideally a dagger. Just look at history and see what all the different types of stickers look like and you'll see that something more like a rapier or a wakizashi is the way to go - especially since you'll need to pierce all that fur and thick hyde; and let's not forget about getting stuck on ribs and never penetrating at all.
Even if you do stick a bear straight in the heart, it would be pissed like something fierce, go into viking-berserk-mode and it would most likely rip you to pieces six times over before it checked out. Look at some videos on pitbulls getting beat to a pulp, while still fighting - never letting go. A bear is like a pitbull but up to 35 times heavier, so potentially it's a pitbull on steroids x 35.
But let's play with the thought a bit more. Get all kinds of knife armor and some really high-pitched sound alarm and with a rapier-like dagger in one hand and perhaps a large Kukri in the other, #&!=ing bash that beast in the nostrils once before he has you in the ground-and-pound position (which will happen instantly if it wants to take you). Honestly, I think you should keep that bear spray anyway, because it's never gonna hurt you the way that bear can. Bears are just as fast as an angry feline when it fights, but way more dangerous, because it's like 3 times heavier than a lion, for instance.
It would be cool if there was some type of emergency instant inflatable helium balloon device, so that one could just go up in the air and out of harms way LOL.
Bears are a bitch and since one can't carry arms in a lot of places where they exist, it is up to the Gods how it'll end. Guns are the obvious choice, but if you can't have one due to legislation there isn't much you can do but use everything you can bring, which justifies the bear spray. In Sweden, where I live we can't even have the bear spray unless we need it as a job tool. So, a hiker can't have it - only reindeer workers, park rangers and so on.