FWIW I just replaced mine. Things I learned: There are two models of accummulators, the black one pictured and a larger bronze colored one. They appear to be interchangeable but I'm not 100% sure if there is some internal/functional difference. When I ordered mine, the larger bronze one arrived. That one needs a special tool because it does not have the nut on top. I used a filter wrench, but somehow tore up the O-ring. So, while I still have no idea how I damaged the O-ring, you should somehow be careful not to :sombrero: otherwise you get a nice high pressure fountain of brake fluid all over your engine compartment.
Once I changed that, the chirp is gone and brakes are fine as before.