1275 timing cover

The 1275cc engine in my Sprite (12V prefix) has no timing marks
on its timing cover at all! They must have been sheared off at some
point in its long history.

So, I cannot time the engine.

Anyone know of where I can get such a cover (used or new) with
the breather and timing marks?

How do I stop the engine from turning so I can undo/re-fasten the
crank pulley bolt in order to replace the cover? Engine is in the car.

Evangelos