For the benefit of some of us, well, maybe only me, you'll have to clarify this.
Soy, is that this black sauce? -if so, what kind?
Linseed bread, I think I can google that, but please clarify!
Would Marmite (the original!) do?
The bread is soy and linseed, as in this recipe though I buy it from the supermarket rather than make it myself.
I would much prefer vegemite to marmite.