Ah I see what appears to be the same nib listed there as "soft," but still curious if anyone has tried it. Not expecting anything magical for $23. I am in the US however, so would likely order from Meisternibs or another vendor and have nib modifications done on this side of the pond.
Some other flex nib providers I know of are The Good Blue, Blue Dew, FPR and Kanwrite. I also know a few nibmeisters that will make/sell custom nibs or pens with custom nibs. I believe Santini Italia may sell a spare nib without a pen also, but I'm not sure if you have to have purchased a pen from them first. The Santini Superflexy was still a bit stiff for my taste.
Another petty good flex nib is the Magna Carta Mag600/Mag650. I have the 650 but the feed doesn't keep up. The owner said he was going to send me a new feed but I haven't received it yet. I don't believe they sell individual nibs, but perhaps Meisternibs will get some eventually as I have seen #8 MC nibs there. At the Chicago Pen show I tried a Mag 600 that was tuned by Les (of Stylosuite), and it was one of the best flex mods I have tried, however he doesn't work on other people's pens/nibs, only sells pens he has tuned/done grinds on. He also had some other nice flex mods. I had my 650 tuned by Matt Chen, but it still railroads a bit due to the feed.
I believe Kirk Speer also made some well reviewed flex nibs but I don't see these for sale currently at Pen Realm. The FPR 14k nib I have heard is really good, but I have only tried their steel flex nib, which is ok, but I never was able to get the feed set well in a pen that wasn't an FPR pen, though I haven't tried in a few years. The noodlers flex nib is not good in my opinion, though it can be modified with a dremel or files to be more flexible (essentially carve it to look like an FPR flex nib).
I'm sure there are more. I was just curious about the one at Meisternibs since I was likely going to order some other nibs there anyway.