Three options I can think of:
1.) I don't know the front cap on your coach, but the obvious easiest way is if you can just add a set of fog lights if there is a fit for spaces in your cap. Add switch, and 12v fog lamps.
Or this:
https://www.google.com/search?q=crea...TF-8#kpvalbx=1
Advantages, you aren't messing with the existing headlight wiring, you are just adding another circuit and set of lights.
If not, then a number of manufacturers create a daytime running light, by electrically taking the regular beams, and install a relay which puts them in series. Effectively then each light bulb instead of getting 12volts to each light, only gets 6 volts.
2.) An RV has an advantage here, in that you may have 6 volt house batteries. If you do, then the simplest way would be to install add a DPDT relay and a switch.
The switch turns on the relay. One input to the relay is the existing headlight power feed. The other input to the relay is a new wire that taps into 6 volts. The output of the relay is the wire to your lights. If the relay is NOT energized, then the existing headlight switch provides 12v power to the headlight. I just described a single throw, the double throw relay would have a 2nd set of contacts that do the same thing for the otherside light, and it flips them both at the same time. If you flip your switch, the relay flips and now the 6 volts is sent to the headlight instead.
3.) If you don't have 6 volt batteries, then you have to get a little harder, in that your relay has to do two things, it has to first put the headlights in series (as opposed to them being in parallel now), and provide power to the pair.
Perhaps there is some aftermarket device which does the same, never looked.
Linear Mode
