Atomic owns Oxygen Snowboards but I doubt they are available in North America anymore.
You can buy them used, on ebay or at Blue Tomato.
You can view their lineup from 2003 (including 2 race boards) at www.oxygensnowboards.com but the website hasn't been updated since then.
But I'm pretty sure that they have dropped the Oxygen name now to go with Atomic Snowboards for good. From what I understand, they thought Oxygen image was too "Euro" for the American market, so as you can guess they no longer make alpine boards.
I used to have a Proton 172 and it was great until an airline broke it..