Along with Lawrence Walker's version, it is worth your time to also check out Aldus' version. Pick the best stuff from both and make your own style. I personally have both of these versions as my guide. When the Ossun is played right, it's hard to beat. A very good song to have in your repertoire, but you got to play it right!
*note, the Ossun Two Step requires a great commitment from an accordion player to learn. Both parts of this song do not come intuitively. Remember, Aldus is playing this version using single button style. It Can Be Found! You just have to commit with an Iron Will!
Oh, and have a listen to Aldus' very last run on this version. Not the melody, but the turn! The man is practically raping that accordion. Listen to it scream. LOL