Although I can't cite the source for what I'm about to say right now, I was told that when towing a car 4-down that only three things are required pertaining to lighting (unlike a normal trailer) and those are 1) tail light function, 2) brake light function, and 3) turn signal/4-way flasher indication are all that are required when towing 4-down.
Exempt functions are the third brake light, license plate illumination, and side marker lamps. Since I use the Unified Tow Brake, my toad battery is being charged so at night, I keep my parking lights on so I have side markers and license plate illumination when I'm in motion but from what I've heard, they are not necessary. This is baffling, however, since I would think both would be required as side marker lights and license plate illumination I believe are required for any other trailer.
So with that said, both a light bar or separate left/right lights should be legal as I've seen them used on toads all over the country.
Light bars from what I remember are quite expensive, however. Here's a company that features wireless light bars and they are all over $400:
TowMate.com - Light duty wireless tow lights
A magnetic left/right wireless setup is about $170:
Wireless Tow Lights
I think you'll be okay with either one but I'll let the more knowledgeable chime in so you'll be sure.
edit: I missed that you said 22" light bar ...that may not be enough spacing. I'm thinking the 48" ones would be the one that you'd need or at least 31"