Just wanted to give a quick post on this guy as it's cheap ($9.99 / £12.00) , and works brilliantly. It's an IR remote, so you do need line of sight to the camera, but it does support bulb mode! I forget how much the official Sony one is, but I remember it was a bit ridiculously priced last time I checked. Haven't tested it outside at distance yet, but it works just fine if you're standing near the camera like you would for landscape work.
US - http://www.amazon.com/gp/product/B00GSAEN4A
UK - http://www.amazon.co.uk ...ase-Control/dp/B00GSAEN4A
P.S. You do need to turn "Remote Control" option to 'ON'.. I think it's in tab #6 (toolbox) / page 3, on the A7R.