bike24.de sell them a bit closer to home. They are probably available in the UK too, I just happened to be putting in an order.
I've been using an Ixon IQ on mine (big 4xAA light), but not for long enough to get any longevity feel. It is sold by B&M for use with their Ixon battery lights (
towards the bottom of this page), so I hope they've got it right. For scale, the wire used is 5mm diameter.
With "proper" mudguards (SKS), and fork crown (this is my Thorn Audax Mk3) the pretty identical Cyo bracket looks like this:-
Fairly tight, although there is a couple of mm clearance between the bracket and headset and the light could actually move down a bit more to give greater clearance.