I know that you posted this last year but Northern Tool gave the following answer: "The O-rings in the swivel have a 19mm inside diameter and are 3.5mm thick."
They are available overnight from Amazon ($5.99) if you're a Prime member. For the next time... :)
Have you or anyone else found a replacement for the 1" ID aluminum hose coupling?
The interior surface on mine is very rough and I don't have access to a reamer...
BTW, the Ebay two prong Craftsman gear puller worked great!!!