All the brands I've looked up have between 4 and 5g carbs...
HOWEVER. 20g of carbs doesn't mean you can eat what you like as long as it's under 20g. Ryvita I think have a lot of fibre in them but still be careful. Cream crackers I wouldn't touch as they're made with white flour which will bump your insulin levels and stall you. There's a list of allowed foods on induction for a reason - food needs to be low GI as well as low carb. Atkins is about regulating your blood sugar. Having the odd thing that's low carb but not low GI might be alright for you, but it's not a good idea to do regularly.
You'll also find there are alcohols which are zero or near zero carbs. However alcohol is a macronutrient so while it may not take you out of ketosis, having alcohol in your system means your body will choose to burn that over fat, slowing weight loss. The less you can drink in induction the better, and not at all preferably for the first couple of weeks.