This refers to South Africa:

I want to sell a 12 year old VW Polo but I cannot find the "Vehicle Registration Certificate" which must be given to the buyer.
How can I get a replacement?

You merely go to the local licensing and testing office. In every major city.

Your appear to be from UK, do you own a car there or live there part time?

Thanks Chuck, this is a South African issue, not UK. But I am out of the country and cannot just go to a licensing office.

I live in America and cannot imagine a public service institution without a website for both services, or contact information. Do you not have those option? Or maybe a local friend or relative to act in your behalf from the locality, and at least give you the proper information on ways to proceed.

My google search of South Africa Vehicle Registration revealed a few possible leads for you to check out.