Based on this product's specifications, here are some alternatives and similar models
Protective case Spigen Liquid Air for Samsung Galaxy Watch 8 40mm, black
Summary description:
Spigen Liquid Air protective case designed for Samsung Galaxy Watch 8 40mm in black. Slim TPU construction provides edge-to-edge coverage, protects against scratches and minor impacts, and preserves access to buttons and sensors. Easy to install and remove, it keeps the watch's shape and allows charging without removal — suitable for daily wear and active use.