There was a DVD release in 2006 that included the original, unaltered versions of the OT. If you can manage to get your hands on those, that'll get you the unaltered OT. I happen to own them, and while the quality is rough as hell, it's nice to have them for rewatching.
Alternatively, you can torrent the Harmy Despecialized Editions of the movies since you already legally own the films. They're technically fan edits and exist in a weird grey area, but they keep some of the background and quality improvements from the later edits but leave most everything as close to the OT as possible, and they're generally seen as the preferred way of watching the films by a lot of folks.
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