The MX with most of the smaller primes will be about the same size as that OM, and it doesn't have small controls either. See here for the dimensions of the various M bodies, the MX is slightly wider as it uses a different shutter to the rest.

The only ones with small controls are the ME Super and Super A/Program A where Pentax decided that little buttons were the future for shutter speed control. Which would be why I prefer the MX, KX, or K2!