Sadly the outlet's issue is actually a pair of threads missing entirely, leaving a gaping hole in the threading.
Double sadly it transpired that the pump was out of warranty (second hand buy) and Swiftech was thus unable to help me out with a new top. The local shop has EK's tops but I'm unsure about their effect on performance. Not being a US based customer I would have to order Swiftech's own top from overseas, which would result in a major costs explosion. And the EK looks rather pretty too... Argh. Such difficult times.