Make room in your suitcase for a bag or two of these:
EAS 100% Whey Protein Vanilla - 5lb
Take a shaker cup with you and just mix with water or milk from the vending machine. Take some McCormick extracts, like coconut, mint, etc. and put a drop or two in your shake. That way you can change the flavor a little, for variety, in case you get tired of plain vanilla everyday.