The definitive map is the 1:20000 Table Mountain map from the 5-map Cape Peninsula National Park series by Peter Slingsby - see www.themaps.co.za. It's a very detailed and beautiful map, with every last boulder and gully marked, endorsed by the National Park and paths approved by the Mountain Club. Also known as "Ziggy" maps, Peter Slingsby's Table Mountain maps have been in print since 1972 (I've got the 1974 2nd edition), and it sure is nice to see them back in circulation, updated and improved. In the same series are a number of Cape Peninsula hiking maps and Western Cape touring maps.
For Table Mountain there are also two other maps that I know of - Shirley Brossey's map, and the Mountain Club of SA's "Approved Paths on Table Mountain" (1993) at 1:12500 scale, which both leave out most of the more exciting routes. Great for keeping the public where the Mountain Club wants them - safely on the ground and out of the newspapers.
A good place for second hand maps (and older hiking books) is the Cafda Bookshop in Werdmuller Centre, Main Road, Claremont. They're tucked away in the bottom of the building, and the maps are tucked away behind the counter and in a courtyard out the back. You can pick up a few gems here if you make the effort.