The choice is becoming clear from the info that's been provided.

1) The limitation of your vision rules out the suggestion of DX P7 due to the fact that the switch has a tendancy to flicker or change mode. That maybe a safety hazzard in your case.

2) You have plenty of supply of AA battery so that rules out 18650 battery.

3) Anything that can fall out of the bike must be remove and that mean a MS will require the lamp and the battery to be remove.

4) Your price range seem to be limited to $50-$75.

I strongly agree with trying the AA Shiningbeam recommended as previously mention. Buy one first and see what is your run time with the battery you have a supply of. You can get the flashlight pretty fast and not like DX. See if the Lumen is adequate and check to see if you may have to use two of those lights. The cost of two flashlight will be $52 +SH. They will yield 2x 280 lumen which should give plenty of light. With one on your helmet and the second one on the handlebar held in by Twofish $16 +SH, it will be fairly easly to remove just the one one the bike when you have to take the bus.

If you do choose this option, I advice you run the two light with the battery drained at different level such that one battery in one light is fresh and new while the second battery in the other flashlight is half depleted, This way, you will not find yourself with two dead battery at once and you only have to carry one spare set of battery.