welcome to the site Kerina, sorry to hear about your 126,
there is a chap called Mick on here forum name (BIS13) he has loads of BIS spares at the moment, he may have a carb for you.
Do you know whats wrong with the carburettor? is the car failing MOT on emmisions? you can buy a repair it for it, but i would go for a another one.
regards
Chris