When the lever broke I went to the local hardware and found that they didn't stock parts. So I decided to make my own replacement part.
Upon looking at the original part it became obvious that it did not seem to be designed to last for the length of the lawn mower. I decided that it needed to be beefed up in the place that it broke and also I shortened the lever so that it was less likely to catch on passing vegetation (this is why it broke last time).
One of the major problems was the the original part was designed to be produced via injection moulding procedures. As I wanted to print the part I needed to redesign it so that it would print properly without the need of rafts or the need to cleanup the part after printing (I like being able to use the part straight off the print table).
I used the original housing that the original lever worked within. With just a small adjustment to this housing the lever works with the ratchet part of the housing so that the throttle stays where I want it to stay.