All of the A1s (including sciroccos) with factory AC use the same type. Some are metal some are plastic but they are interchangeable. I doubt you will find them new anywhere.
you might find some direct replacements on early Audis but I dont think they ever used the same exact box... A2s are completely different but you might be able to adapt them.
I'd just post which one you want on here and in the classifieds and one of the many who seem insistent on ripping out the AC units will have one for you.