Jonno said:

The Empire teaser sounds like an apt choice - what's the best source for the McQuarrie version? The 2004 bonus disc?

I guess the one on the 2004 bonus disc is in best quality but it's quite severely cropped, here's a comparison with the 4:3 version on the Editdroid extra features DVD.

Original '79 teaser in 4:3 - Editdroid DVD:

Original '79 teaser in 16:9 - 2004 Bonus DVD:

It also seems to be a different variation from the one found on the editdroid extras DVD as it lacks this crude early logo at the end:

If this bother you, I would suggest the second '79 teaser mislabeled as Launch Trailer on the 2004 DVD, that one is in very good quality. I don't know, maybe there's a better version of the original teaser on some fan disc out there.