My company has been that way for years, so this has always been a concern of mine. I don't leave keyboards there because of what I pay for them, so I take them back and forth.
The main keyboard I use at work is the HHKB Pro 2. As far as typing goes, it is the ninja, the silent assassin of keyboards and it works as good in Windows as it does in Mac and Linux. Plus it is the quietest keyboard I own.
I also take the Filco with browns there. This keyboard is louder, so I get some looks, but never anything too terrible.
This is handy because these are the normal keyboards in my rotation and thay are both really nice.
The Cherry ML4100 is another quiet mechanical that I like, but I don't own one right now. When I did own one, I just left it at work because it was cheap, then I broke the plug. Oh well. The reason I haven't replaced it is because the HHKB is so easy to take to work.
So there you have it, my recommendations. Now, I don't know what type of office you work in, and at work I am surrounded on all sides by professional writers so typing is easily forgiven, but I think any of these keyboards would work for you.