Here's a semi-fast way to farm for the Flamberge, depending on your item discovery. It's 100% worth it though because the Flamberge is easily a top tier weapon, especially since you can get it so early.

With 107ir like I had it'll most likely take a while but if you're doing it late game with 300+ir you'll get it in a couple of runs (most likely).

(Sorry for some bad editing, it took literally an hour to farm for this)