Yes. Go2Africa uses www.bagport.co.za for both airports.
Johannesburg's luggage storage depot is located in Terminal A. The number of the airport desk is +27 11 390 2317; the number of the storage facility is +27 11 390 2689.
Cape Town storage facilities are located on the ground floor at parking area level 2. The contact number is +27 72 384 2954.