I have the following sets on eBay for auction, if interested please check it out.
Lego Space Set 6877 (Jear 1990) - Vector Detector: Complete, parts like new, with original building instruction.
Lego Space Set 6833 (Jear 1990) - Beacon Tracer: Complete, parts like new, with original building instruction.
And additional parts from the set 6811, but not complete.Status at the moment is: EUR 1.00
with kind regards, Guenther Leitner