If you have a Polish delicatessen handy you might be able to find chleb proteinowy from the Mestermacher. It is not like the bread we know, it is a small pack of 5 thin slices weighing 250 gm, but it is possible to make cheese on almost toast or dip slices into an egg, or put kippers on. It is expensive, but it is only 7.5 percent carbs. (weglowodany) I thought it was 7.5 gm per slice (kromka), my Polish is not good - but no 7.5 for two slices. It doesn't toast like white bread, and the butter runs off, but for cheese on hot bread it is better than nothing. It is also high fibre (bialko, I think) I put the slices into the toaster for a bit longer than a normal bread but I suspect that it would burn rather than toast, and go dry and brittle if heated for too long.