Anker makes a decent one, which can be bought for $20 or a bit less. Should be said it is the only vertical mouse I've used, but it works as a mouse and I haven't had shoulder tension/aches since I started using it.
Honestly, I was, indeed, refering to that one. I dind't know anker was doing one, but it is the same generic that many brands are selling. It's optical and not laser, therefore precision is mediocre and the battery doesn't last too long like the laser ones. Also the construction materials feel pretty bad. I mean, it's what could you expect from a cheap mouse. But again, the normal mouses have much better mouses and with laser sensors for similar prices.