I have been fighting the same battle. I Believe you can do it and I have a hunt booked for July 2025.
There is a black powder brand call Obatex that can be bought by your outfitter around Johannesburg.
From what I read it is hotter than goex and they recommend you back off on your load and work your way back up.
There is another brand that they sell on the western cap but I didn’t research because it is way south of where I am hunting.
My guy has already bought a can of FF and I will grind some of it up to use in my pan.
As far as getting the gun in the country, I hired an importer to meet me at customs. I expect I will have to also give the customs guy a $100.00 bill as I have had to bribe them about half the time to get them to give me my bow.
My suggestion is either to go with my outfitter who has powder or have whoever you are going with send you a picture of the can he has. If it is not someone you know, you could end up over there and they have a can of pyrodex
Back in the first decade of 2000, I used to arrange trips to Africa for wingshooting. They would typically come into the Cape and spend a few days there and then travel up to Johannesburg. If they were $$ heavy, they'd take the Blue Train from Cape up to Joburg on an overnight run. It's a very posh, everything included, overnight trip. Johannesburg is not (was not) a safe place, especially in the financial district after about 5PM. So we would book our folks into a one or two night stay in Rosebank, which is a suburb of Joburg. It is/was patrolled by it's own security and has all the amenities for shopping, movies, etc. that you'd find in any modern suburb - basically a safe and pleasant area to stay overnight or for a few days.
Travel was by train to begin the wingshooting expedition. A steam engine took the Edwardian Coaches from Praetoria (adjacent city to Joburg) up into Botswana on the first part of the journey. Then it would switch to a modern diesel engine pulling the train. The train would arrive at its destination sometime that night and in the morning the hunting lodge would come to the train to transport everyone to their estate for the day. Typically hunted in the morning (driven hunts); had a very nice mid-day meal; hunted in the afternoon; and returned to the train for a formal dinner. That night the train would move to its next location. This went on for 5 to 7 days depending upon which package and dates they bought, and everyone was flown back to Preatoria from Botswana.
They often took extensions staying at some of the luxury camps along the Okavango Delta to view and take pictures of the wildlife, which are more abundant there than just about anywhere in Africa. Some went into Zambia afterwards to visit Victoria Falls from the Zambian side because Zimbabwe was a dangerous place to stay back then. Staying in Victoria was usually OK because it generated lots of tourist dollars, but Zambia was much safer. However if you are not hunting in Zambia, you can't get a permit to take your guns in with you. So we had to come up with an outfitter who would hold the guns while they were in Zambia and bring them to the clients at the airport in Botswana for their flight back to Joburg.
Having the proper gun permits is a big deal in South Africa, Botswana, Zambia, and Zimbabwe.
MOST IMPORTANTLY - before you leave the US, you need to take your firearm(s) with you to your closest Customs office to fill out and sign the form (sorry, forgotten the form number), which they will stamp, listing all your guns as your posessions so you don't have any trouble bringing them back into the US when you return. Back when I was doing this, the governments of South Africa and Botswana accepted that US Customs completed form as a gun license and you could not bring your guns into those countries without that. In South Africa everyone must have a gun license for each firearm they possess and they accept that completed and stamped customs form as a gun license from the USA.
So make sure your "importer" has done this before successfully or you may be in for a very rude awakening because they don't make any allowances or leave any lee-way in the enforcement of their gun importation and/or possession laws. Have your importer give you the step by step process so you can be confident your gun does not get confiscated for illegal import into the country. That customs form is key to getting everything to work.