As in, something that won't essentially turn itself off due to vibrations/bumps. I've got a AAA unit right now, but the light gets a bit wonky if the body is shaken/rattled a little too hard.

when I 1st started commuting a few years ago, I was using
a planetbike 1/2 watt Blaze. After a few years of use, no
issues other than the weak beam(2 watt version is available
now). so I replaced that with a 100 lumen flashlight, used that
for a few months no issues. still I wasn't happy. now I'm using
an 18650 powered flashlight and I'm kinda satisfied.

AAA powered flashlight review with drop test and water submersion test,
available at Costco:

Sounds like the current light you have has bad connections. If you can solder, I would recommend doing that to make sure the connection stays solid. If the battery is rattling, you can try wrapping the battery once with tissue/toilet paper to make it more of a snug fit. If the spring in the back is not doing a good job, you can always use a spacer like foil, paperclip or whatever conducts electricity. Coins are good for flashlight barrels but I don't know what type of light you have.

The Costco one is a alright light, but I think it takes 3xAAAs. I believe it essentially runs the three batteries in parallel to get similar outputs to what a 18650 can deliver but will have a much shorter runtime. I am with 1nterceptor and use 18650 cell flashlights mounted on the bar for light. It's pretty bright

Sounds like an light form the "old days." There's no reason - except needing $30 to get a good light without battery rattle....

Such as? Not 8opposed to going the 18650 route, but I have a number of AA and AAA rechargeables already.

Dozens of Surefire, other "unknown" brands at $30...... Many from Wally MArt of Target.

Good lights at ~$50-60 Fenix LD20 Eagletec PA2 - many more - do a search "2xAA" good flash light - I mean how hard is that?

https://www.shiningbeam.com/servlet/t...P-dsh-G/Detail