I didn't have anything about the immobiliser with my car either but it said Toad on the fob itself.
This is the company I ordered the spare from: http://www.southerncarsecurity.co.uk/index.php?route=product/product&product_id=63
It was just a question of reprogramming both the existing and the new fobs with the immobiliser, in the car. I didn't need a pin number or anything.
1991 Eunos Roadster 1.6 silver stone, blue hood.