How about Veggies pier, the pier southside of Uvongo lagoon, Margate pier (open?), or anywhere you can access a jetty at one of the southcoast 'lagoons"?
There are also places where you can get close to the beach with a car, like under the bridge at the Umzimkulu mouth at the Sandspit or just round the corner south of St. Mikes. You can also get right to the beach at the Port Edward launch site. People can carry you to the water or pull you in reverse on your wheelchair.
What about off the side of any of the many boat slipways when not too busy?
Also ask Echo7 on this forum