an XML of some sort.. available for as little as £31 to £95 from DX, though reports suggest that quality & spread improves with price… but £30 you can get a lot of light if your willing to wait (delivery from HK).
Also consider MTB Batteries (Smudges) XM-L unit, not as cheap but UK supported & a very good light (I have one). I use mine with a Trout Mini (4x XPG LED unit) to great effect – you “maybe” don’t need this much light, but it great to have it!
DealExtreme XM-L bike lights:
£30.95
£31.04
£31.44
£33.05
Though the two below are only reportedly 1000 lumens & those above are 1200 lumens, there the same LED and will be as powerful. They will actually try and sell the orignal P7 900 lumen units as 1200 lumens in some adverts now….
£52.33
£92.16
Another option is a “normal” XML torch – £24.08 though you’d still need to get a mount for your helmet.
Though my friend with a MJ-872, happily uses an orignal P7 Magicshine bike light quite happily with his…