This brand on Amazon called "Raw Grass Fed Whey" is high quality and comes in a bag. I can't post a URL because I'm new but it's a brown bag with a cow logo on it. You could just put this inside a freezer bag for added protection and throw it in your checked luggage without having to worry about bringing a large plastic container but still have conspicuous sealed factory packaging. It differs from country to country but you're usually allowed to bring dried unopened food internationally. I have Celiac Disease and so often pack gluten-free food in checked bags if I'm not sure I'll be able to find it where I'm traveling. So I think you'd be fine with this. Possibly in a carry-on too, but if you're brining more than 12 oz. it has to be placed in a bin for additional screening. This company also sells a 12 oz size though. Maybe for that exact reason.