I don't see the same spoiler on that site as the one the poster is looking for. The one that I see is the one designed to fit that fiberwerks front end treatment (personal opinion in regards to appearance of that part kept to myself). That one will not fit the standard 944 8V valance.
Are you saying he has the part he is looking for, it's just not on the site? If so, a lot of 944 8V owners will be beating a path to Fiberwerks door.