As good as Hi-Viz gear is, I think that the amount of surface area visible from the front (especially at a distance) is somewhat limited. If you do not want a headlight modulator I think that fork-mounted LED lights, in amber, may be your best bet. Fork leg mounting will provide the triangle of light that seems to make it easier for the eye to notice and recognize. Locomotives for several years have supplemented their bright-as-hell headlights with a pair of lower-mounted lights that help folks notice that something is coming at them.
I know that you don't want to sacrifice any extra electrons to lighting, but Whelen's TIR 3 and LIN 3 lightheads only draw approximately 400 milliamps each, or less than one ampere total. The TIR 3 heads are directional, while the LIN 3 heads have much better off-axis visability. The TIR heads are somewhat brighter, at least to my eyes, as the output is more directed.
I would set them to steady burn. A flashing pattern would be eye-catching, but would not be legal here in Montana (and probably many/most other states, too). I tend to agree with other posters that amber seems to stand out better against the visual background clutter.
You would have to fabricate mounting brackets. 1.5" aluminum angle is readily available at hardware stores and home supply stores. It is pretty cheap and easy to work with, even with simple hand tools (hacksaw, handheld drill, and files). A TIR 3/LIN 3 light head is 1.25" high. It will fit either on the outside or the inside of the 1.5" aluminum angle. The TIR 3 lighthead is made in a vertical format as well as a horizontal format. The vertical format would give a narrower profile, and not be as prone to get bashed against things. It may be harder to find a supplier who stocks the vertical format TIR 3 lighthead, however; if you find them somewhere, they may be more expensive than the commonly available horizontal format lighthead. The bracket fabrication will be a lot easier with a vertical head, since you can just use the one leg of the angle stock to bolt to existing mounting tabs on the fork. (A brake caliper mounting bolt is the most common example, and the solution used by folks such as MotoLights.) Don't try mounting a horizontal lighthead in a vertical orientation; the optics distribute the light all wrong for being seen by other motorists.
If forward conspicuity (being seen by on-coming traffic) is the issue, I personally would go with the TIR 3 version of the light. The TIR 3 is less likely to cast light into the eyes of adjacent motorists (same direction), and will not glare as on-coming traffic passes you. I use the LIN 3 heads as hazard flashers on my airhead BMW, where I want a wide-angle light, but use a TIR 3 as the auxilary brake to keep the light more focused directly behind me.
Please note that there are several other brands of similar "Gen 3" LED warning grade lights available in the marketplace. Fred W has noted (in another thread on LED brake lights) a brand that has a high intensity/low intensity setting, which may be a good option if you ride at night more than occasionally.
). In addition to my own HiViz gear both Mark and I have 
