I have an Admore lightbar on the back of my bike. It flashes for the first second, then stays solid. I've never had any problems with LEO's.
I think it's this one:
http://admorelighting.com/store/index.php?route=product/product&path=61&product_id=56
I think it's this one:
http://admorelighting.com/store/index.php?route=product/product&path=61&product_id=56