Fix/replace immobiliser

My immobiliser has broken off the key and is at risk of getting lost. Any ideas where I can get a replacement? I'm having difficulty uploading a picture to the computer but could text it to anyone who would like it. Thanks.
If its the key fob with buttons I'm not sure as is k11.
But sounds like you need a replacement key shell.
A picture would help other members to tell you what is the best solution for this.