Trying to adapt something a little different, intended for a Ducati, and only $16.38 new, might be worth a gamble:

Search for its title, on ebay: "For Ducati Monster 620 695 696 750 1100 1200 Rear Brake Master Cylinder Pump New"
Since Ducatis do not have integral brakes, this is probably a small-diameter cylinder. It comes with a reservoir.
By the way, I like integral brakes and wouldn't recommend disintegration. But you're not asking.