The two ways I know of doing a thatched roof in our scale are, either to use plumbers hemp, or roll out modeling clay to the desired thickness, then use a comb or such like to create the thatch effect.
4Ground /Italeri use humanely harvested teddy bear fur for the thatch. Actually faux fur is quite popular now and I have seen cheap cushions made of it. Primark may be a good source or jumble sales for teddies. Tip of the year - try a good electric beard trimmer on the faux fur (trumptoupee) or hemp eg a Philips with variable depth/length settings. BTW plumbers hemp has been used in scale modelling for a long time ever since the Pendon model railway* took vernacular architectural models to a higher level of accuracy and realism. On that layout it still looks brilliant. I think PTFE tape is used a lot by plumbers now instead of hemp as it is safe for potable water piping.
In the UK the straw colour of thatch doesn't last long with rain and pollution but I wonder how long it lasted in 19th c. S. Africa?