Best place I've found for the trigger at the mo is on eBay. Item number: 130126212792
The watersop connector to fit it also on eBay. Item number: 230158331652
Before fitting it to the pole, carefully remove the tubing attached to the front of the trigger.
Fitting it to the pole is a piece of cake. Most of the pics I've seen of them on the net aren't complete. They don't show the mounting bracket that comes with them. It's clipped off the picture. They're made to fit on the tube of the numatic george carpet cleaner so they fit nicely straight on the pole. I've strapped mine on using large cable ties aquired from Maplins. The mounting bracket has two slots iether side of the mounting bracket which are perfect for slipping the cable ties through. I've fitted a third on the front of it for extra support but this is probably not necessary.
When it's fitted to your pole, in my case down near the base, extend the pole fully before cutting the pole hose to the required length. Leave yourself a reasonable loop of hose before cutting it and attaching it to where you removed the hose that came with it. The connector on the input side is a quick release one. If you want to use this (I found it very useful for transporting and carrying the pole) you'll need to purchase the above female waterstop connector. If not, then remove it and replace it with the brass connector taken from the end of the black hose you removed from the trigger (discarding the ball bearing valve from inside it).
Here's the pic of mine again,
Hope this helps,
Mark
Poll