This is a nice simple case for the SmartLCD display with 6-7mm knob post, built-in chirp speaker, and SD card slot on the left side. The SmartLCD comes with many RAMPS kits, including one from Gadgets3D, which is where I got mine as part of their full RAMPS 1.4 kit.
Two optional 3mm screws can hold the SmartLCD in place inside the case, or just insert the LCD into the top part first before adding the bottom part. The top and bottom are designed to fit together so no additional hardware is required.
I printed this case in natural PLA and it works really well. I had to file down the tall posts in the back a little to get a fit where the bottom didn't bow, so I may bring the verticals inward a little on the next revision.
There are lots of great knobs posted on Thingiverse, or you can use the one that comes with your SmartLCD. I used the one from DeltaPanel by scottmayson.
The smartlcd.scad file is from my own measurements. On mine the speaker was mounted on the back. This is an option in the scad file. You can compare my SmartLCD model to the one by sola_technical.