I received my order of 3 Stalker masks a couple of weeks ago, from meshmasks.eu. It took some time to get them, and when talking with the retailer he indicated that there are problems supplying more. Brassguard seem to be the current must-have airsoft item.
Another option is Cleric here in Calgary from the JOC boards. He has made a very nice facsimile which he is selling locally.