I'm guessing that if he's close enough for spray you are supper. 12 gauge slugs or heavy rifle bullets at the first sign of trouble might work. I've never had a hostile encounter with a bear but I've seen them cover a good bit of ground pretty fast. I'm betting he can make 15 or 20 feet per second.
A grizzly bears speed is 35 MPH. Phil Shoemaker stopped a grizzly bear charge and killed the bear with a 9mm shooting 147 Buffalo Bore's +P Outdoorsman Ammo
Yeah, but Phil can shoot!
And the bear was after his clients, if I understand his story correctly. Double the reason for your companion to be armed as well and effectively as you
Colossians 3:17 (New King James Version) "And whatever you do in word or deed, do all in the name of the Lord Jesus, giving thanks to God the Father through Him."