As of today (14th September, 2021), the torch-xla-1.9 wheel has been fixed, as reported in the GitHub Issue tab (#3121).
So, now anyone can just use
!pip install cloud-tpu-client==0.10 https://storage.googleapis.com/tpu-pytorch/wheels/torch_xla-1.9-cp37-cp37m-linux_x86_64.whl