I had to search for quite some time, as nobody in North America had or could get any, but it looks like there are some Givi Y306 wingrack fitting kits for the B4 still available in Europe!
I ordered mine from the Czech Republic, and although there was 6 weeks of silence after I placed my order, after the 6 weeks they actually e-mailed me a tracking number, and sure enough, a few weeks after my kit arrived in Canada! Amusingly, the box says "Yamaha" on the side - looks like Givi failed at printing the labels for them, but the contents were correct.
Note that this is JUST the bandit-specific fitting kit, you'll have to supply your own Wingrack (or Wingrack II like I used) - these are readily available in the used market or even new still. Bandit is now ready for touring with 3 Monokey hard-case mounts!
I got mine from RDMoto, and with the Czech Krona being pretty weak right now, it ended up being quite cheap - with shipping to Canada, only ~1400 Krona, or $56usd shipped! Within the EU I'm sure shipping would be cheaper.
http://www.rdmoto.eu/cs/product/421/31307Pics fitted to the bike, along with some closeups of how it all fits together for if someone ever finds a used one and has trouble fitting it. I swore at mine for a while until I figured out how it all went together (further compounded by the fact that the Wingrack unit was used and missing a few fasteners)
Note - the Y306 fitting kit INCLUDES the optional Givi Y100 universal 'bridge' kit which ties the bottom of the two wingrack sideplates together. I would have no qualms about sitting on the rear rack or hoisting the bike in the air with it. It's that strong. It's tough to see from my pics, but it's a huge steel bar that goes underneath my license plate holder. It's the shiny bits bolted to the very bottom of the black wingrack side plates.
Normally it's ~$40-50usd alone, and I barely paid that for the entire Y306 and Y100 kit together (brand new!) It claims it's only needed if you're not using a top plate, but I installed it anyway. Nice to know it'll still be bulletproof even if I pull the top plate off, which takes like 30 seconds and is only 4 allen head cap screws anyway.
http://www.happy-trail.com/Products/GIVI-Universal-Wingrack-Bridge__GIVI-Y100.aspx