I've not spent a massive amount of time looking, but I didn't find anything. The nearest bouldering that I know of is the Robberg in Plett, but I can't vouch for the quality as it was probably 6 years ago that I was last there and I'd just started climbing.
I've done bits and bobs on Robberg. Theres a nice wall just round to the left as you come down the steep bit of the path with a bit of traversing on, you need to avoid falling on the bench though. A bit further on from here, there are a few obvious boulders just where the path leads right and down to the beach. There are a couple of obvious boulders with some nice probs, and on good rock. These are all on the conglomerate rock. I also did a fairly highball arete on sandstone with big pockets off a wave cut platform, but would struggle to remember where. It wasn't far from the beach on the W side.
AFAIK climbing is not allowed though, so be sensible / keep a low profile and avoid entering any archeologically sensitive areas. And beware sea and waves!
There might be some stuff around the Knysna heads, the rock quality might be a bit dubious though.