I’m a huge fan of the Kensington Trackball in the middle in between my halves. It’s not especially subtle or cute but it’s very comfy to use. I think the slimblade is smaller, not sure. Also, I love mouse keys. I use them for all small movements that I can, and the trackball for larger movements. I would love an app that like, subdivides my screen into a grid that I can use to just automatically jump to a place with just my keyboard, that would be perfect.
TBH though, especially if you’re a frontend dev on Mac, you will still need the trackpad or Magic Mouse. Gestures are kinda not replaceable, as far as I can tell.