A very kind officer, having heard my outpourings, immediately reduced my R200 fine by half. However, he told me that he could not reduce it any further as this required the authority of a magistrate or traffic prosecutor - which meant presenting myself in court.
Since it would probably cost me more in terms of time spent to go and plead my case before the appropriate authority, I decided to cut my losses and pay the 100 bucks. (PS: The above image is the bracket on the back of my Vuka, clearly showing the "missing in action" licence disc. The replacement disk will be firmly taped to the INSIDE of my carrier box!)