They are rare as hens teeth, although some say a Polo or Skodo sender will work, Try the classifieds here, vwvortex, thesamba.com as well as a general search.
I have found that a VW only parts store in Auburn Washington has a lot of new and used parts. also Beaver creek auto in Beaver Oregon is a good source. Beaver Creek has tons of VW's!!Hi I have a mk1 1990 rabbit cabrio. Trying to source a fuel sender unit for it. Any help/advice please ?