Try memoryexpress, it looks like they stock some silent cherry mx switched keyboards.

Memory Express has a pretty good selection, I'd try there.

I was at a ME not long ago; I tried my hands on everything on display; they all make a sound. Some are good about not making a sound when the switch goes down, but the key makes a sound when bouncing back up, if your finger is completely off it. Space bar keys are particularly bad. A keyboard isn't silent if the space bar isn't.

You seem determined to be disappointed so I don't think I can help you. People in the mechanical keyboard community obsess over the sound; what you're asking for is like asking car enthusiasts for a silent car.

Is there a specific reason you need to buy in person? If you need to get a feel for the switches beforehand, many online retailers have switch samplers for about $15 USD. That being said, those don't cover spacebars.