There's a private party seller on eBay selling his new Ion 10/12 with a brass drag knob. Try messaging him. He might sell you the knob separately. He's including it with the new 10/12 for only $75 shipped. I'm thinking $12 shipped for the knob to Canada sounds fair. You'd probably be doing him a favor if you bought the knob from him: He could, in turn, reduce his price to $65 and sell the reel already.
And about the brass knob 'throwing the balance off': With the brass knob installed the reel will still stand on its foot without tipping over. Mounted on a rod there is a slight tilt when holding the rod through the swing or drift. It's not an annoyance, as it's hardly noticeable. From my perspective it wasn't, at least.