Talk to Kraft first. You might be able to get one made without breaking the bank, but not without breaking trademark law. Do you really want to be a mobile advertisement?

Vegemite is one of those things that you need to be introduced to (indoctrinated?) at a very young age. Vegemite on toast is often a young Aussies first solid food. My boys (2 & 5) love it - so do I for that matter.