There is a couple going to the beach at Kleinbrak in the evenings from time to time. You should try to hook up with them. They post on the Dogging pages: Western Cape, but unfortunately don't give a lot of advance warning (so you need to keep checking that page). Post on the same Dogging page, and provide your profile name (it's here anyway on the Forum!), and ask them to contact you by PM? Should be worth a try! And only a little further than Hartenbos....
PS I have some good memories from both the Hartenbos caravan park and the Kleinbrak Motel!!...