Is there a direct drop in replacement for the DS1235ABW-120?

The drop in replacement for the DS1235ABW-120 will be the DS1230AB-120+.
  
W in the DS1235's suffix denotes a low profile package.  This package type is not available for the DS1230.

The + denotes lead free/RoHS compliance, the AB represents the 5% voltage tolerance, and the 120 represents the 120 read/write access time of the SRAM in nanoseconds.

The DS1235 battery life expectancy was 5 Yrs, and the DS1230 battery life expectancy is 10 Yrs.