They are not available in the US either. They were discontinued at least a year ago, and existing stocks are gone. Bike Bandit continues to show them on their inventory, and when you order them, the order proceeds normally, but then two or three days later you get an e-mail from Bike Bandit saying that they are no longer available. I've personally talked to 30 dealers trying to find them in a local inventory, but with no luck.
There was a set that showed up last year on ebay, but they wanted twice the original msrp. Someone eventually paid it and they sold. Since then pickings have been slim.
The best bet to get a set would be from salvage of a front end crash where the rear of the bike was OK. Since there aren't a lot of Rockets out there, and since they only made the pannier guard rail kit for 1 or 2 years, I expect it won't get easier to get a set.
We have laws in the US that require that a manufacturer stock parts for a vehicle for 10 years after its date of sale. Since Triumph included the pannier guard rails as standard at least one year, I'm not sure how they're getting around this issue.