I came across a short scene with girl-on-girl handgagging in episode #37 of the 2nd season of Story of Saiunkoku, aka Saiunkoku Monogatari. The young lady receiving the handgag is the same one that was cloth-gagged and tied to a pillar in episodes #6-7 of the 1st season.
The 1st season has been released on region 1 DVDs. The 2nd season has not, but is available fansubbed.
Story of Saiunkoku, 2nd season
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