Yakima Skybox just fits the Crosstrek. I think its only slightly too large but not worth selling and getting a smaller (less useful) one. : r/Crosstrek
Yakima SkyBox 21 Rooftop Cargo Box Review - 2017 Toyota RAV4 Video | etrailer.com
Yakima Skybox 21 Rectangle-Shaped Carbonite Roof Top Cargo Box w/ SKS Lock, Black | Canadian Tire