hi George,
i am originally from Weenen , KZN.
sorry i missed this for so long.
when in south africa i really struggled to get help as well.
but anyway, here are some trees you can try.
white stinkwood, makes a great bow, treat like hickory, cut in the spring, split the stave, bark will peel off, seal ends and back.
the bugs love it, so be careful- spray with some kind of bug killer.
make the bows wide and with a flat belly- just like hickory. trap the backs and toast the belly.
makes a great bow. easy to find nice long , straight pieces.
Mulberry- common old garden mulberry is awesome too.
find someone with a pecan nut orchard- treat like hickory.
many of the acacia species. "Tortillus" will make a good bow, and possibly "Karoo"
although not an acacia- looks very similar- Dichrostachys cinerea
it is very good i believe!!
https://en.wikipedia.org/wiki/Dichrostachys_cinereagood luck boet!!