How do I get the joke weapon to get the achievment that corresponds with it?

[Baron of Nothing]

I've already beaten the game on Normal difficulty, No Timer, and Challenge, yet have not once come across it. How do I find it and is anyone else also having difficulty finding it?

[dyra55]

I found it during my Hard playthrough, on the first 10 floors or so

[Corkinio: Dumptruck Aficianado]

Try replaying the game on a difficulty you already beaten. Reload the final boss chapter, there's a weapon roll select in the beginning.

If it's not there, retry until you get it :)