I have had check airmen qualification on the 777 three different times. Long story but I was in an out of the training center as an instructor on four occasions at my airline.
I also did some training/checking on the side with FTI in Denver. You might give them a call as they are always harvesting guys from across the street at DENTK to do checks and contract training for them.
It's been a few years so I don't know what their deal is on the 777 at the moment.