The original cross is currently housed in the Library of the University of the Witwatersrand, and was declared a National Monument under old NMC legislation on 6 May 1936.

The Dias Cross Memorial is a provincial heritage site at Kwaaihoek, Alexandria in the Eastern Cape province of South Africa.
 
A minor road turns sharply off to the right from the main road that leads from Alexandria to Bushman’s River Mouth; it passes Boknes and comes to an end near the coast. About a kilometre further east from the end of the road, beyond the sand dunes, lies Kwaaihoek, also known as False Island, a high promontory that juts out towards the sea. On top of the headland that extends the furthest Bartholomew Diaz, the famous Portuguese navigator and discoverer of the Cape, erected a cross or padrao here, on 12th March, 1488. A replica of the cross has been erected on the same bleak, exposed spot.
Geolocation
-33° 25' 48", 26° 22' 12"
References

Government Gazette of South Africa

Further Reading

https://www.sahistory.org.za/dated-event/portuguese-navigator-bartholomew-dias-erects-first-stone-cross-south-african-coast