Q:

Surface mount troffer on ceiling

I found these 2x4 LED troffers at a big box store. I'd like to surface mount them on my basement ceiling. I have low ceilings and they are only a half inch thick. They would be perfect. Can you think of an appropriate u-shaped bracket, corner bracket, or rail I could mount to the ceiling and then slide these into? They weigh about 3kg/7lbs.

A:

so you plan to get 2 of 4' pieces of C channel and screw it to your ceiling 2' apart then slide the troffer in from one end.

not to scale 
possibly you could use two of these drop ceiling edge moldings
 riveted together to form a C
Else you could get a sheet-metal place to fold C channel for you, or see what you can find in aluminum extrusions.

