No street lamps in town? Borrow some!
If you have Resistance, you can turn on object ID tags in the editor. Find some lampposts in other towns no one is using. Let us say, one of them is #142364. Put object 142364 setPos and where ever you want the lamp. No addons needed aside from Resistance. I am not 100% sure this will work, but I think it should.
One problem! When you change the map by moving map objects around, they stay gone until the entire map is reloaded (or was this fixed in 1.90?) If it was not fixed, then if the player, for example loads another mission on the same island after playing yours, the lampposts will still be moved. I could only suggest that at te end of the mission you put the lampposts back where they belong, which will not catch it, however, if the player does not finish the mission.
I hope you find a better way than this, LCD.