Get a whole harness kit and tap the control actuation wire to the high beam like the old days.
I bought some PIAA LED 4800K for my S60 main lights , they are more daylight colour suitable for fog and good for my eyes (years of TIG welding , I need yellow to see....) Philips have kits too. JW SPEAKER and Stedi sell good quality too.
A light bar is bright white light and will reflect off the fog and blind you unless you put a yellow/orange filter on them.