Oh, turns out the Coinbase API does indeed support it:

See https://api.coinbase.com/v2/currencies (search for ZAR)

So we can just use https://api.coinbase.com/v2/prices/BTC-ZAR/spot as for the other currencies!

So this is the place where one should look up such info:

https://docs.cloud.coinbase.com/sign-in-with-coinbase/docs/api-currencies