On a low carb high(er) fat diet, it isn't really necessary to snack as you body should be able to manage better with the fat you eat keeping you satisfied for longer. So it's worth while making sure that you eat enough at meal times.
But if you do snack then any finger type low carb food, including small quantities of high % cocoa chocolate, should do the trick. You could also look up recipes in our low carb section or on Google for "fat bombs"!
Robbity