The lost cut version of the cantina is available in much higher quality on the 2011 Blu-Ray set (and many subsequent releases).
Those outtakes come from the digital version of the ‘Making Of’ Star Wars books by Rinzler. They’re probably only marginally better than that YouTube video of you grab them straight from the source, unfortunately.
And as for the Jabba scene, I believe OT.com user Bobson Dugnutt was attempting a better recreation of it. I don’t believe he has finished it yet. And it will probably never be completely seamless as a portion of the scene only exists with scrolling credits over it.
Let me know if you need help finding anything else!