Sorry you did not get "the" answer you were looking for from me.
I answered the best I could, because the fact is that we all have hinderances/hardships/etc., and our own problems to overcome.
We do just that, we overcome.
I don't know your daily situation enough to be able to "tell" you exactly what to do.
As well, your information is ALL OVER the place in regards to consistency. In your first post you say you can drink a shake on the bus (protein/fat) then later you comment, "I am not allowed to eat on the bus". Last I checked, by food they mean NO eating/drinking of any kind, so how you could have a shake on the bus, I've no idea.
As well, if I had to do it, I'd mix oats in my shake or make them in a seperate container and eat them cold/dry/hardened in a container on the bus w/a shake if I had to. If a shake is acceptable to be consumed on the bus, who the h*ll is going to see you throw a few quick bites of oatmeal in your mouth?
I've eaten a footlong sandwich and a half a large pizza INSIDE a movie theater where "outside" food isn't allowed, and have done so many times.
Point is, it can be done, so get it done.
~SC~