I was moving the lawn, and I reversed, and had a loud thunk. Immediatly shut the engine down (Well, throttled up to full chock, and stalled the engine, which is a different problem I think)

Anyways, the little wheel on the deck had popped off, and I ran it over when I reversed.

It's a simplicity 4211h. I foud the wheel online, but I can't find the retaining ring... anyone got a part number? (The orginal retaining ring is somewhere in the lawn)