Your best bet for your price range would be looking at an r5 light from Shiningbeam and look at 18650 cells.. You would still be well under you 100.00 price point. Most lights that would last as long as you need would be in the 50-100 lumen range to give you the long runtimes you are asking for.. The R5 is right at 300 lumens out the front, quite a bit brighter than what you are using now.. I would buy 3 cells, each would give you right at 2 hours of runtime in high mode, they are easy to swap out on the road, takes about a minute..
If you want a AA solution - I have a fenix l2d - duracell nimh charger - cells and lockblock available.. This is 1/2 as bright as the R5 light, but does use AA batteries. Send me a pm if interested..
But for best brightness/long runtime look at this:
http://www.shiningbeam.com/servlet/t...4-II-R5/Detail
charger:
http://www.shiningbeam.com/servlet/t...Battery/Detail
extra cells:
http://www.shiningbeam.com/servlet/t...e-18650/Detail