My grandma still drinks Bonox lol. It sounds absolutely horrible! Still love vegemite anyway. I live near the Vegemite factory in Melb and take in lots of deep breaths when I drive past... yum!
As for healthy alternatives, Freedom Foods makes a "Vege Spread"... it has no wheat/yeast etc that's in vegemite, although I think the salt content is rather similar. I also get the Country Life rye bread (dark rye or soy-lin) - it is more expensive but it has a lot less carbs than regular bread (I think it's only 30% carbs, whereas a lot of other breads are 40 - 50%) and is also free of wheat and yeast. I don't eat butter/marg either... don't need it I reckon
Oh and there's another that I am yet to try. It's made by a company called Empower foods - it's a low carb high protein bread
You just buy the bread mixture and have to bake it yourself. Sounds very interesting. Knowing me I'd turn it into a rock and have to eat it with a hammer... but I might try it one day anyway