Grateful Mikrotik supplies rack ears for the CRS112-8G-4S-IN product.. I have a few of these and have no idea why they do not come with ears(and they are not available from your suppliers as an aftermarket item). I also have a few CRS212-1G-10S-1S+ IN units which do have ears(I'v stolen the ears off those to put onto the CRS112's.
While I'm bending your ear, perhaps consider removal of the LCD for the above mentioned units, as I have them rack mounted, the LCD is a bit of a waste..!!