Not the definitive answer to your question but UK (the largest RHD market by far) figures were:
1989 45
1990 174
1991 64
1992 10
1993 2
However (confusingly) the following figures are in the Haynes 'Audi Quattro' book of a few years ago:
Production UK Sales Comment
1988 610 319 First two of 20V in RHD
1989 462 140 385 were 20V RHD
1990 413 186 All 20V (RHD figure not shown)
1991 - 64
1992 - 10
1993 - 2
So a guess might be 400-450?