bummer.....
the clutch arm may or may not stay put. vibration will probably make the clutch arm fall off.
you could contact the person you bought this from, for parts.
you could post in Buy/Sell/Trade, for a replacement part. (with this pic) somebody might have a spare sprocket cover w/ clutch arm, lying around.
you could JB weld the area where the bolt broke, solid to the clutch arm....wouldn't be pretty...but it would hold for a while.