Maytag Control dial cap disappeared

Some mistery happened to my washer. The cap disappeared and couldn’t find it anywhere.

Even if I find it, I’m not sure whether this is the only part I need.

Currently the dial has this part on.

This is a pull out switch, so without the cap, I can’t pull the knob out to start.

Please tell me what parts do I need. The cap should be connected to the pull-out tab sticking out the center rectangular opening of the above part, timer knob.

Thank you.

Those caps are hard to pull off, so I would get both parts in the diagram below

http://www.appliancepartspros.com/partsearch/model.aspx?model_id=5170396&diagram_id=28465360#d28465360