Hi there

Yes, your quite right.  The part you are looking for is:

Remote Commander Reciever (IR-R100)

Dimensions (approx.) 46 x 19 x 45mm (w/h/d)

Unfortunately I have been unable to find this part either.  Therefore you have 2 options:

1. Try contacting Sony Support : HERE (to see if they can find it)
2. Connect a generic IR repeater to the back of the unit, see below:

Looking on Amazon, I found this:

http://www.amazon.co.uk/Marmitek-Eye-universal-extender-cable/dp/B000MBY1FC/

There are many others if you search for "IR Extender"

Hope that assists

Cheers