ML-3 Remote shutter release
It works, but the cables gets very stiff in low temperature. You can use the BULB feature of your camera. But when I have to use long shutter speed, I use the MC-36. But again very stiff cable in low temperature.
But you may take a good look at WR-R10, WR-T10 and the WR adapter WR-A10.
Nils Petter Rognstad