Little rubber part of strap the end goes into so it doesn't hang down

I have a Forerunner 225 that I use all the time. The little rubber thing. you push the strap end into when you are putting it on your wrist broke. Now the strap just dangles off my wrist and doesn't hold the watch securely. How can I find a replacement for that little piece and instructions for removing the strap from he watch so I can slide the new piece into place?

Thank you!