If you can track it down, check out La Dernier Séance - it's the full Paris show from which MIE tracks were taken. Once you hear the whole set, it all works so much better (apart from Hughes' incessant whooping and hollering - I wouldn't have minded them editing that out).
http://www.discogs.com/Deep-Purple-L...elease/2240489
For Rainbow, there were a series of albums released from the 1976 European Tour, at least one of which did include Stargazer in the set.
http://www.discogs.com/Rainbow-Live-...elease/1883350
Both of these are official releases, cleaned up and professionally mastered by the DP Apprec Society, and fully approved by the bands, so they're way better quality than official bootlegs. In fact, I'd suggest they sound better than the mixes on MIE and RoS.
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