Try Alfa Service in Germany, according to their on-line shop they seem to have the original rubber original bushes for both Alfasuds and Alfa 33s. from memory their website is
Alfa-Service.
Hope this helps...
BTW, I have urethane on all bushes on my 'Sud. Good for handling, though I suspect that road noise is increased.
Andrew Matusiewicz
1983 Alfasud Ti QV
1971 Alfa Spider 1750