Hello eits1000.
if you are still looking for seals, this thread on the german Barchetta forum may halp you.
http://www.barchetta-forum.de/smf/index.php/topic,18707.100.html
On the last answer (at this moment) the user "awastel", who sells new seals for the Barchetta, informs about the prices.
das Set Verdeckdichtungen (3 rechts, 3 links) kostet 385,00€, die Verdeckkastendichtung kostet 125,00€ und das Set Türdichtungen (1 rechts, 1 links) kostet 100,00€...
The set of roof seals ( 3 right, 3 left) cost 385€, the seal for the roof bonet costs 125€ and the set of door seals (1 right, 1 left) costs 100€.
The Barchetta has 3 generations of roof seals, if you use the same generation on all the 3 seals, there is no problem. If you mix different generations, the seals may not make their work correctly.
Hope it helps you.