Protein Drink Shaker

Can anyone recommend a good shaker cup for my protein shake, because the upper end of the shaker cup (where you drink a protein shake) always opens in my back and my gym protein shake is all in my sports bag.

I recommend Highley www.myprotein.co.uk proteins at cheaper prices and great if you use this code if you are a first time buyer u get an extra 5% discount on your order hope this helps, you can buy from here much cheaper high quality whey £ 10.49 per kilo, the more you buy the cheaper it is also excellent