Stores will stock what people will buy. If your store suddenly stops stocking your favorite low carb item - or doesn't have it in the first place - here are some options.
Talk to Customer Service
A store wants to make money. If you are actively wanting to buy things, they will want to sell them to you! It might be that the company itself discontinued the item. In that case you're sort of stuck. It might be that the store's distributor stopped carrying the item, so the store can't get it through them any more. You could talk to the company directly and see if another distributor in the area carries it. Finally, it might be that the distributor still has the item, but the store thought nobody liked it. This is of course the best out of the three situations, since the item is still around and available to the store. Talk to them and tell them how important the item is to you.
Find Other Stores Online
Let's say that situations 1 or 2 are the case - and your store simply cannot get that item in any more. You have to find another place to get your hands on it. Do a search online to see who else will carry it. You might find another store locally which will suit your needs - or you might find someone you can mail order from. You often get a discount from mail order firms, and it could easily be enough to cover the shipping costs. It's well worth a try.
Contact the Company Directly
Find the website for the company and email or call them. Explain your situation and ask them what can be done. They might know of other stores in your area who can help you out. They also might be able to sell the items directly to you. If anybody is going to know where their product is available, it will be the company themselves.
In the end, low carb product companies only survive because people buy their products. If you find a product you love, tell your family! Tell your friends! Buy a lot of their product and show your support. That will help ensure that they stay alive, prosper, and are able to continue to provide you with what you love.