Immobiliser key?

[jmec]

Hi. I have a 'The Immobiliser Advanced Anti Theft System' fitted. It works fine but I only have one key which is in the form of flat plastic key with 8 copper contacts sunk into a clear plastic insert. This fits into the female fitting just above the headlight angle adjuster, below the dash R/H side. There's a credit card sized card, with the car's history, with a 'Immobiliser Assistance' code number plus a phone number which is not recognised. I'd like to get another key as the original is looking worn and I may loose it! Any ideas please?