There really is nothing low carb readily available on the shelves that I have found in the sweet pastry line.

Many of us have used the "muffin in a mug" aka MiM recipe to make something sweet or savoury to substitute.

I make a sort of bread using ground linseeds.

My recipe is
4 Tablespoons ground linseeds (flax in the USA)
1/2 teaspoon baking powder
1 Tablespoon oil (I like coconut oil or toasted sesame oil or 1/2 oz melted butter)
1 egg

Melt fat or oil if needed, mix with egg then add the dry ingredients and let sit for a minute to thicken up.
Spread out on baking parchment or put in a microwaveable container and microwave for a minute or so till cooked.

If you want it sweet you can add some artificial sweetener.
I tend to prefer savoury so sometimes add some grated parmesan and/or herbs or spices.

You can adapt this recipe to use more or less ground linseed, or use ground almonds or coconut flour insted or as a mix to vary the taste and texture.

I like it because though not actually being the same as regular bread it does the job of bread. It only takes a few minutes to make too.