Also, Burger King issued glasses for all three movies so there should be some commercials for those. The years would of course coincide with the release years of each movie.
I seem to recall the Proctor & Gamble commercial for the free posters with the purchase of certain Proctor & Gamble products. This would have been for Star Wars in 78.
General Mills cereal had commercials for the Star Wars stickers in boxes of The Monter Cereals, Coco Puffs and etc. These also would have been in 78. General Mills ran commercials for the cereals that had Star Wars trading cards in them. Again in 78.
Cheerios ran commercials, for the posters that were inside their cereal. This was 78 as well.
I think those are about the only ones that I can remember. Most of the cereal commercials were of course ran on Saturday mornings. I do remember seeing a few of them, but I don't recall specifics. Hope these help.