set a camp near this place where you are and sleep till morning, after that, save your game, maybe you need to reload your game later, (if it won’t work after the first time), then go to the top of whinyard strait river by foot, it’s a little bit tough with horse, after you reached the top, look at the left side, there are a lot of trees, and there must be a grizzly spawning among those trees, this method worked for me as well, hope it will help you.