First little hurdle, I had a 31.9 M900 front derailleur lying about from a Zaskar frame I sold.
Not sure who invented this kind of system but I'm lost to why, maybe it has some physics properties that actually improve shifting but I highly doubt it.
Since the original piece was not on the bike I used one I got of a Concorde Kudu, it's plastic, hasn't got bearings so I might ditch it altogether but I need it for mock up. I tried to look for a similar part with bearings (bushings?) in metal but only came across one here from a post made in '13.
But this isn't going to work well, the way it's set up now. But it'll have to do until I can sort something else.
First two is from the interwebz and that's what the original looks like.
The third is mine.