This is an odd oversight, and I couldn't find any commercially available harness that serves this purpose. So I just made my own harness! I used the car charging cable that came with the SBV (which seems pretty useless to me anyway). I cut off the the end and added my own solar connectors. A fairly simple DIY cable. Just be sure the cable can handle the amperage from your solar panels (shouldn't be a problem unless you have a TON of solar power coming in).