The largest amount of bears I have ever found is 6, in 2 different places:
Thais: Cave South of the White flower temple (where spiritual blessing is bought):
Orc Fortress: North East corner of the main floor inside the fortress:
My advice: If you haven't done the Orc bestiary, I would go to the orc fortress spot during a rapid respawn, leaving a fire in the top west corner of the imagen (cover all that area of fire until you find the sqm) and keep killing all the floors upstairs. The one in Thais is goo, and near the town, but you will have to wait upstairs without doing anything until you got the respawn back.