Sorry Guy, but that is going to be pretty much an unobtanium device. Good though it is polarised, so a regular 10uF 250V radial electrolytic will fit nicely in that clip, and then you only have to extend the leads with some nice sleeving to match the holes. See the other 2 with rubber bungs next to it, change them as well. The glass sealed ones ( C5) will last forever, or at least they will outlive the rest of the unit.
The colour change is an indication of the oxide layer thickness, and the missing electrolyte is a lovely sulphuric acid blend, to keep the oxide film stable.
At least the 390n units are easy to get as 400V rated parts now, and will do nicely there space wise.
ps you have a parcel winging it's way to you.... Even has a note inside for you to enjoy.
Edit: What do you know, RS has the perfect replacement, even fits the clip and looks like the original as well..
http://za.rs-online.com/web/p/aluminium-capacitors/2267081/RS 226-7081 10uF 200V axial cap, 105C rated as well. ESR is good enough ( 10R) and lifetime at 105C is a year. Keep it cooler and it will do better though.