TodoSync is a tool that sync google reminders directly to todoist.
You can check out the free hosted version using at todo-sync.atymic.dev or self host
on your own server.
Feel free to post bug reports as issues and i'll look into them :)
At some point i'll write some documentation on how to get up and running on your own server :) For the moment, have a go and create an issue if you get stuck.