You can use a MAX232A if you replace the four capacitors with .1uF capacitors instead of the suggested 1uF capacitors. The MAX233 doesn't require capacitors, but it physically will not fit in the same space as the MAX232 (the MAX233 has 20 pins).

The MAX3232 works with 5V or 3.3V, but is quite a bit more expensive in DIP packages than MAX232s. It also uses .1uF capacitors. You can use a MAX3232 with the RS-1 to allow it to work with 3.3V or 5V equipment (the default for the RS-II).