It basically looks like a cross between an Elecom Deft and a Logitech M570 or even Logitech MX Ergo

if you dont care about anything but the buttons and price (how well it works, it feels, HOW the remapping is performed) then maybe an elecom deft https://www.amazon.com/ELECOM-M-DT2URBK-Trackball-Finger-Function/dp/B0171QQ7IY thats quite a few buttons for ~$30