Two best are Dinove Edge & IBM model M... I have both and I prefer IBM (buckling spring is priceless when you grook it)
Unicomp still makes buckling spring keyboards with IBM's Model M (as well as other IBM) designs. They're loud as hell but feel great. http://www.pckeyboard.com/ You can ask them for Mac keycap replacements to swap out the ctrl/windows/alt keys with control/option/command keycaps. Works great on my Mac with swapping Alt and Option key functions in the keyboard preferences panel.
I work in a semi-open plan office. I was concerned about this last year when I got my Unicomp keyboard.
I've been assured by my peers that the sound is noticeable, but not loud.