Check out Holosun HS512GD Reflex Sight Low-poly 3D model on CGTrader for $6. High-quality mesh by Akinaro: 5300 polys, 2700 vertices. PBR, Textured, UV Mapped.
BLEND (Blender, filesize: 111 MB), BLEND (Blender, filesize: 111 MB), OBJ (OBJ, filesize: 112 MB), FBX (Autodesk FBX, filesize: 111 MB), DAE (Collada, filesize: 112 MB)