There are hundreds of Icom CI-V level converters on the web, here is another one. For a comprehensive collection about CI-V issues check Ekki`s (DF4OR) site.

There is nothing special in the schematic. Its all SMD, the level converter is actually a MAX202CPE (although MAX232 is written) because 100 nF ceramic condensators are enough for the charge pumps while MAX232 needs at least 1 uF. The whole stuff is powered from the serial interface, I have tested it with two laptops and it worked.

The board was designed 1998 (today I would do it much smaller), shortly after I bought my IC706. In the pictures above it is magnified, the actual size is 15x17 mm and fits in a standard SUB-D9 housing. The actual size drawings are here: top layer bottom layer (mirrored) top layer parts bottom layer parts