That jacket was from about 3 seasons ago and is pretty much sold out everywhere now. However thanks to the Bond movie they are re-issuing it in January. If it fits anything like the original ones then you might want to get a medium if you plan to layer it but i would suggest going to try it on first.
Yeah, they are releasing more of them, and I've recently been notified that I can preorder one in the next couple of days. Problem is I can't try them on, because it's a preorder. I'd describe my build as lean but athletic (I do a bit of lifting and running), I think (read: hope) they fit like the originals. For clarification - you'd recommend a medium? I'm not planning to layer a ton, but I was wanting to have it fit well over a simple sweater and shirt two layer (as I guess I'll mostly be wearing it in cooler weather). Thanks for helping a guy out. I'd have no idea about the sizing without some useful advice.