Part x431c01 Electric, IR Transmitter Tower, USB with Black Front. This is for the first Mindstorms series using the 1.0, 1.5 or 2.0 RCX. This tower works with the 2.0 software. There is also a patch you will need to get if you are using one of the older versions.
Here's the tips I have for programming the RCX 2.0
Windows XP 32 Bit Virtual Machine using Parallels or Virtualbox
You can find the iso of the Robolabs online to install it
Getting the Driver the IR tower is the most difficult task, however,
i just looked it up on line in drivers tab "online", and it found it. despite it being windows xp,
so actually pretty simple.
Don't get Windows 8SE, the graphics that come with the VM don't meet the requirements for the Lego Robolabs software to program the RCX 2.0.