The only brand name case available in stores is from Incipio. It's just a simple gel case and not very protective. Best Buy sells a clear version, while Target sells a smoke grey version. Otherwise, you'll only find Chinese brands on Amazon or eBay. This is my favorite, fairly slim, yet protective, and a snug fit:

Moto X4 Case, Taorey Ultra Thin and Slim - Shockproof Drop Protection - Anti Slip and Scratch - TPU Leather TexturedScratch-Resistant For Motolola Moto X4 2017 (Black)… https://www.amazon.com/dp/B07CH8BD4G/ref=cm_sw_r_cp_apa_i_jQBzCbGPBRQG3