GNC, Walmart, CVS, Walgreens, etc. Many drug, grocery, and superstores have different types of Protein shakes.
I use unjury which I get from www.unjury.com. I love their unflavored and chocolate. I mix the unflavored in with other foods. I use powdered milk and ice with the chocolate. I mix it to the thickness of a wendy's frosty for a treat. YUM!
I also keep slimfast high protein cans in the frig for a quick fix when I'm running crazy.
There's a website where you can try samples of different shakes for a small fee.
Good luck!!