Joe Rocket Motorcycle Jackets

You can also try a shoe repair, many of them do repairs leather .........

I'd take a dry cleaner who specializes in leather, and have them replace the button / eyelet / SNAP

If you bought in a store or cyclegear www.cyclegear.com they replace the item or send it to fix it for you

Button or Snap?

If it is a button, so you can sew on a leather needle - in most cases, you can find the holes that the first button used.

If it's a blink of an eye, it will be replaced professional - as mentioned before dry cleaning specializing in leather, or go back to Joe Rocket.