I've lived and worked in grizzly country since I moved to Montana back in 1975. My first 3 years at a remote Forest Service Ranger Station in NW Montana, and since '78 off a county road 6 miles from Bozangles. We've seen grizzly tracks in the snow 300 yds from my house.
For many years I carried a Ruger SBH 7 1/2" .44 magnum while hiking, fishing, or hunting. In all of that time, I've only encoutered 3 grizzly bears outside of Yellowstone NP.
I saw the first grizzly bear while I was driving on a remote logging road south of Eureka, MT. It was feeding on some fresh green, early spring vegetation along a creek about 100 yds below the road. I watched him feed for about 10 minutes while I was still inside of my truck. I then got out of my truck and sat down on the edge of the road. I didn't sit there more than a minute when his nose went straight up in the air as he got my scent, and he took off running up the hill on the other side of the creek.
My next encounter with a grizzly was on a back country trail south of Big Timber, MT. The previous fall a horse had broken it's leg there and had to be put down. The next spring a grizzly found the horse carcass and claimed it. A local outfitter used that trail to take fishermen into wilderness lakes, and his packstrings had been charged by that grizzly.
So, as the Forest Service blaster, I was called to "remove" the dead horse (one of many that I had "removed"). One of the Ranger District employeees went in there with me, and when we got to the dead horse, the grizzly was there feeding on it. He ran away as soon as he saw us, and when we left, there was nothing left of that horse bigger than a Big Mac which the birds, coyotes, and that grizzly would finish off in a day or two.
My 3rd grizzly bear encounter was one year where two friends and I were hunting and camped at the end of a Forest Service road near West Yellowstone, MT. We had the quarters of 2 bull elk and a bull moose hanging in the stock rack in the back of my pickup. Before going to bed one night I went outside to check my horses, and no more than 10 yds from our tent camper, a grizzly on top of the road cutbank, woofed and clicked his teeth at me.
He had a radio collar and an ear tag, and we later found out that he had been a problem bear near Cooke City, MT and had been trapped and relocated to where we were camped. I had my Ruger .44 on my hip, and I fired one shot over his head with no effect from him. So I fired another shot into the trunk of a pine tree next to him, and again, he just stood there woofing and clicking his teeth at me.
So I holstered my .44 then bent down and picked up a golf ball size rock and threw and hit him with it. He then ran off into the darkness and we never saw him again.
I have since bought a stainless S&W Model 626 4" .44 magnum that I practice shooting it almost every week, and I have developed full cylinder length shotshells for it that I enjoy shooting Skeet station 8 clay targets with it.
As others have posted, while hunting in Africa, your PH is usually right by your side and carrying a large caliber rifle. Unless you actually want to hunt your African animals with a pistol, I don't think that it would be worth the cost and hassle of bringing a pistol there, just to have one with you.