'My night vision is not good, so really want to find a good light to try and counter that.'
Andrew,
Buy a Dinotte 200L light - (4 Cell Lithium Ion version)
currently $283.20 at
CRC
Expensive, but one of the best things I've ever bought.
(A lot cheaper than a number of the top end lights)
3 modes in constant beam
High - Run Time 8hrs
Medium - Run Time 16hrs (good enough for all riding except high speed and dark wet nights)
Low - Run Time 32hrs (good enough when riding with a group not at the front)
Also has a variety of flashing modes.
Quality of engineering is extremely high. (Made in US)
Total weight 315gms (battery pack fits on top tube 230gms)
It also comes with helmet mount although I would want the 2 cell lithium for this purpose (less weight)
Cheers
Perry