vauxhall can prob make one up if you give them the chassis number, however i had a key made for my nissan from what they had on their computer and it didnt work even though the ignition barrel was the original. if i were you i'd just buy a new (or secondhand) barrel and key off ebay or something,
As the key has to be programmed the best way is to go to your local Vauxhall Dealers and let them sort it out, cost quiet high, I think I paid about �85 for mine plus programming.
look in yellow pages and u will find loads of mobile key people for instance attend a lock, nash locksmiths etc etc they hav computers on board and can cut and code 90% of vehicles these days ...hope this helps