Q:

How to fix or replace the timer button of a microwave oven?

I have a microwave oven which timer button is broken. I would like to fix it (by using glue?) or replace it (with a similar "key"). The oven is a Samsung M1714.
However, I am afraid of making things worse if I try to repair it, and I do not know any shop where I could buy something similar. I noticed there is the number 3 written on the inside of the broken piece.

Do you know an online shop for this kind of thing? 
Here are several shots:

A:

I have repaired dials similar to this in the past.
I have found that if you apply some CA glue (super glue) or epoxy to the crack, and then wrap the outside of the shaft tightly with electrical tape, it will hold up under most circumstances.
Failing that, it appears that you can buy the replacement knob from several online suppliers.

A:

You can actually repair this knob with resin + fiberglas. You can see the final result here.

Hope it helps.

