Wipacs are the cheapest and fairly well made. worth taking apart and running a bead of silicone between adjoining plastic "cups" to ensure a good seal and no water getting in. Which is pretty common on cheap lights.
If your down south, get yourself to Trago Mills. I seen em cheap as there. Failing that, maybe someone in Kernow could buy you one and mail it. failing that, Devon 4x4 have a big stock of them. Picked mine up from billing show last year for £8.50, they have lots. most wipacs i have seen are 55w halogen ones. go for a flood over a spot, obviously.
G