I'm not sure what is blocking your upgrade, but I would recommend to use newer version of gRPC pairing with newer `grpcio-testing` package. I think we have maintained the backward compatibility decently.
Besides, you can install `pip` packages without their dependencies with flag `--no-deps` (considered as a hack).
Sorry, there isn't any link to old artifacts, as people answered in SO, you might have to build it yourself.