I have the same ones, and I got them on Amazon: https://www.amazon.com/gp/aw/d/B098QZM2HP?psc=1&ref=ppx_pop_mob_b_asin_title

I have a Moonlander, and use the keyboard itself for most of my “mouse” needs. You can do the same on the Sofle: https://github.com/qmk/qmk_firmware/blob/master/docs/feature_mouse_keys.md

I also have trackpad between the keyboard halves for scrolling while eating or when I need to make ultra-fine selections. For gaming I use the left half of the board and a mouse in my right hand.