USB Switching

So, at the moment I have a desktop, a laptop and a raspberry pi all plugged into a single monitor through a HDMI switch, this is working great seeing as space is a bit of a premium in my current living conditions, but the main problem I'm having is the mouse and keyboard.

I got the HDMI switch so I can easily work on different devices as needed, but I haven't found a way to switch inputs easily. I've tried Synergy before and found it to be overly laggy and painful (Wireless networks, woo!)

I'm wondering if anyone has found in their travels a USB switch, basically what I want to do is have a single hub that I can plug a keyboard/mouse into (Could probably get away with just the keyboard if needed) that would allow me to switch between input being sent to the desktop/laptop/raspi quickly.

Any help is... Helpful?

Just use a standard KVM that has USB. You won't need the video I/O on them as you already have a HDMI switch.