Do you find that buttons can be expensive or you can't find a matching button?
Then try this simple idea.
Materials needed.

Trace your shape

Mark holes for punching

These holes are used for sewing your button on.
Sewing View.

Colour your plastic button, optional

Now to crochet the cover for your new button

Using the magic ring technique (this forms a tighter close for the beginning ring)
6 sc into ring, (do not join rounds through-out)
2 sc into each sc around, (12 sc)
1 sc through back loops only in each sc around (12 sc)
1 sc through both loops around (12 sc)
Place plastic button into your crocheted work
sc 2 together around (6 sc)
Fasten off leaving long tail for sewing.

Beginning side

Finishing side

Thread tail for sewing

You sew the button on from either side up or down, it depends on the look you want.
When you are sewing on your new button, coming out from the top, you may need to weave under to get to the next hole, so as not to expose you sewing yarn.
These are some buttons I prepared earlier for a neck warmer I made

Now this is a simple button to make, it can be made smaller or larger by adding or subtracting the sc from your beginning ring and also by subtracting or adding more sc rows.
You may want to dress up your new button a little, by using your knowledge of crochet techniques.