Cateye omni 3 for the rear. It uses AAA batteries, has a run time in full that's actually worth having, and is pretty cheap.
You can get a saddle rail mount for it, or you can put it on the seat post.
Front I use a cateye Gvolt 25+, but only cos I have it knocking around. I've tried various lights, and it's the least worst on the Brompton.
I keep meaning to try the supernova Mini on there, but it ends up with a cable into the jacket for a battery, and faff.
J