From wikipedia:

Glucosamine is naturally present in the shells of shellfish, animal bones, bone marrow, and fungi.

Basically, it's in everything you need to make a great stock, instead of taking a supplement!  ;)
It's most likely in insects like locusts but even I am not there yet. I'll try some other day.

I tried natto with rice for breakfast last week though. I don't know what locusts taste like, but they must taste great compared to natto, which is soybean fermented with Bacillus subtilis, but I didn't find anything very subtle in that dish... Before you ask, it's not the same kind of soybean that is grown in the U.S., it's much smaller, so that the bacillus can penetrate deep inside, and it's in the shape of a small kidney, not a ball. There's apparently a unique form of K2 vitamin in it, MK-7, that's not in any other food. I eat enough cheese and miso for K2 vitamin, but I thought natto's Bacillus subtilis would be a nice complement to rebuild my gut flora...