I've given a few alternatives to the Calvados in the post. You could also substitute cognac or brandy, which will make it a somewhat different drink. If you want to add apple flavor, use apple juice rather than the wine.
Apple bitters can also be added to the drink too. And if you top it off with a spritzy pour of sparkling apple cider (or a touch of sparkling wine, if you'd got an open bottle), I don't think anyone would mind.