The Tackeria in Wellington had them in stock in the spring. I'd call them and see what they have in stock because there was way more selection on the walls than what's on their website. But I saw at least 7 different weymouths (in everything from stainless to Sprenger) in a 6" in the store.
No problem! I was surprised to see so much selection in that size but my friend who was there for the whole season laughed at me as apparently the polo ponies sometimes get wider bits than is 'normal' in dressage. There were all sort of prices too.