Not sure if you can still get a new one, but the S410 from Air Arms loads the mag from the left and you could at one time have a left hand stock but only in walnut, and the action can be converted to left hand bolt that closes down properly. I have one from 2002 but with a custom stock.

I also have a S400 long series with FAC air tube in a left hand stock but with that rifle I prefer a right hand bolt as the scope has a large sidewheel and loading from the left would be awkward.

In my gun cupboard there is a Daystate Airwolf with a left hand bolt and they can have the mag load from either side. The stock is an ambi but after some mods including a raised cheek piece http://i.imgur.com/py4FGE5.jpg I'm very happy with it.