Reddit mentions of Arkon Camera Bike Motorcycle Handlebar Mount Holder for Sony Samsung Panasonic Nikon Cameras

$15 pole: http://m.harborfreight.com/2-in-1-support-cargo-bar-66172.html
$8 mount: https://www.amazon.com/dp/B00PICAE4C
$10 mount: https://www.amazon.com/dp/B00585CLVS
Both mounts work great, solid. First one needed some glue to lock up an unnecessary spring-tensioned adjustment mechanism, fine after that

What light do you have? Lots of them have tripod threads, and mounts for those are pretty common - here's one example on Amazon.

If your light doesn't have the standard 1/4" thread, you'll probably have to 3d-print or otherwise DIY some sort of solution.

You could get a cheap camera and a mount that has the 1/4"-20 thread on it. That would keep it handy.

I've used RAM mounts on different bikes/cars over the years and they are pretty nice.

https://www.rammount.com/part/RAM-B-231ZU

https://www.rammount.com/part/RAM-B-201U

https://www.rammount.com/part/RAP-B-379U-252025

These mounts can be pretty pricey, but they are solid. My friend puts them on his ATVs to hold his GPS and has never lost a GPS yet. I use a similar setup for my action camera mount and have programmed the action camera to take a quick picture whenever I press a certain button. I've caught shots of deer crossing the trail with relative ease many times, and find myself using it to take shots of interesting things since like you I find it cumbersome to pull out the phone to take a picture.

I'm sure if you shop around you can either find these components cheaper, or another manufacturer that would be cheaper but still provide the same thing.

Edit: just some quick googling....

https://www.amazon.com/Motorcycle-Handlebar-Samsung-Panasonic-Cameras/dp/B00585CLVS

There are floor-to-ceiling poles that extend and stay in place with a very small footprint, but I think they're generally more expensive. You'd need to get a tripod pole mount to stick onto them, as well. I haven't researched them, but you would want something like these poles and these mounts.

I personally am opting for the light stands that /u/libertytoast posted, they seem to be the best bang for your buck, and then you just need a ball-joint attachment for tilting the sensors. I got a more heavy duty one, here.

My experience with handlebar mounts is to try to keep the device too far from the handlebars. Depending on the weight of the device, the vibration of the handlebars and wind increases dramatically if it's too high from the handlebars. I personally don't think damping solutions like sponges would really help stability. I use this cheap camera mount for my onboard video. When I had my heavy digital camera on it, video kind of sucked, but when I bought my Contour and put it on the same mount, it turned out a lot better. And yes I know it doesn't help that I ride a thumper =p

I like helmet mounts more because of the flexibility, but if you don't have a separate mic or something to cut the wind noise, those videos won't have your nice engine sound except at stops.

Can you not use rubber spacers or some rubbery tape to fill the gap to keep it in place?

I'm totally blanking on the terminology, but my bell clip has this rubberised material inside the ring to kind of fill the space/keep it in place. You can see it inside the ring on this random mount.

I am using these fully adjustable ceiling poles:

http://www.amazon.com/ZipWall-ZP2-ZipPole-Spring-Loaded-Barriers/dp/B002RL8OE4?ie=UTF8&keywords=zipwall%20zp2&qid=1462268219&ref_=sr_1_1&sr=8-1

Spring loaded at top, no vibration and has pads to ensure no slip on hard surfaces.

Along with these handlebar camera mounts:

http://www.amazon.com/Arkon-Motorcycle-Handlebar-Samsung-Panasonic/dp/B00585CLVS?ie=UTF8&keywords=Motorcycle%20and%20Bicycle%20Handlebar%20Mount%20for%20Cameras&qid=1462268311&ref_=sr_1_1&sr=8-1

all works flawlessly :)