The potato chip bag option would have plausible deniability. I would go for a whole lunch bag with sandwich in genuine tin foil as mylar film doesn't seem that thick to me.

Plausible deniability is really important if one expects to be frisked. Traveling in something like cycling gear could be part of the disguise, you can go through special gates at train stations and not be ticket inspected by machine. Nobody expects the guy in fluorescent clothing travelling at 15 mph.