There are DOT legal replacement headlights uniits available, but still pretty dang costly. No H4 (or any other replaceable bulb type) headlight is DOT legal using anything other than a normal matching incandescent replacement bulb. No HID or LED replacement H4 (or 9006, 9007, etc) "bulb" to install in a standard headlight reflector assembly is DOT legal for public road use. And probably never will be: DOT headlight certification is for the original unit as new or with exact spec (incandescent/"halogen") replacement bulbs. So far, no LED or HID replacement bulb has met the DOT beam specs or been submitted for certification - and the way the rules are written it's likely that any non-incandescent bulb is unacceptable.