Yeah I ran into these solutions but unfortunately I can’t seem to find any USB-CEC adapter other than the Pulse Eight, which doesn’t seem to ship to Australia in any economical manner.

I ended up getting a Flirc USB, couldn’t get the existing TV remote to work with that (once paired with the TV it stops sending IR signals, and the TV wouldn’t let me select the PC input as needing to activate the IR mode on the remote), ordered the Flirc Skip 1s… and now that’s working well enough we’re using the Skip1s as the primary remote for the TV as well. About 150AUD down the hole for this solution, and it’s not truly turning the PC off, but close enough!