It will set you back a pretty penny, but I believe this is what you are after:
https://servicesales.sel.sony.com/ec...&itemID=678596 At the moment, the site says they are in stock.
Otherwise, you might settle for a near fit from a place like:
http://www.stylisource.com/pda-stylu...pda-stylus.asp. Maybe measure the diameter of the opening and see if the alternatives provide that spec.
I have the 900 and can tell you the Ds' are to wide for it.