Just mount the light upside down so it is mostly invisible from the sides or above.
The smaller lights I am thinking of are going to be much less effective. Think of it this way: Will your bike look better with a slightly bulky light, or will it look better under the wheels of a dump truck?
What I'm trying to say, and you alluded to, is that this is a very small compromise to make for your safety.
One other suggestion - find or make a light-mount that is fastened under the front brake caliper. A light down low by the front tire looks neater than a light on the handlebars... in my opinion, anyways, but I also think that bike would look better with full wrap fenders
Edit:
Here is an example of the type of thing I am suggesting. With this one, which I believe is made for a particular dynamo powered light, you could adapt for any bar-mounted light by cutting a narrow piece of wooden dowel and drilling a hole through it to act as a 'handlebar' on which you can mount your light. Making your own out of a bit of sheet metal or an old rack bracket would also not be too difficult.
https://www.chainreactioncycles.com/.../rp-prod202150