I found that I like the powdered protein shake mix MUCH better than the ready to drink kind. I used Syntrax nectars, mixed with unsweetened vanilla almond milk (I like the Almond Breeze or Walmart/store brands better than Silk). I know it'll take time to order it, but you are probably looking at 4 weeks of liquid diet (2 pre-op, 2 post-op) so you will need to find something you like- or at least don't actively hate. I bought a shaker bottle at Walmart, the kind with the metal-coil ball in the bottom, and everything mixes pretty well.
For a savory option, I made my own chicken and beef broth. Roast the beef bones on 375 for about an hour, then simmer them in bouillon broth (I got mine at the Dollar Tree) with onion, garlic, carrot (can't remember if I used celery or not). Drain out all the solids and keep the broth (you'll probably need to remove the fat layer after the first chilling). You make the chicken the same way, except I used the carcass from a grocery store rotisserie chicken (I always freeze the carcasses when we are finished with the chicken- but you could buy one, pick the meat and freeze it- some day in the not-too-distant future you'll be able to use it in soup, stew, chicken salad, etc.)