Hit the message boards. There are lots out there that are loaded with "Star Wars geeks." Make friends, ask around. You will not be able to get these in stores. The mighty heads of Hollywood and Mr. Lucas himself frown upon this sort of thing. So be wary. Start with the forums at OriginalTrilogy.com, StarWars.com and FanEdits.com.
You may need to make trades with other eager collectors. What you trade is between you and your new best friend.
The best place to find special versions of flicks that may or may not be on the "up and up" are conventions. Check out the vendor tables at comic book and science fiction conventions. You'll find a lot of weirdo goodies. This can be pricey if you need to travel but if you love "Star Wars" so much that you're searching for EditDroid DVD's then you're probably going to conventions already anyway. The science fiction news site, io9.com, updates a monthly calendar of conventions. Keep an eye out.
The internet is your friend. Search, search, search.