A rather crude bodge, I'm afraid - the rear mudguard on my Brompton broke. For the last year, at least (I forget) it has been held together by a wire coathanger, cunningly wound around the mudguard stays & crimped in place, & some reflective gaffa tape.
Mrs Bs road bike has a dynamo headlight (brake bolt mounted), fitted with a plug compatible with the battery pack from the good old Smart twin headlights. With a 6W bulb, it's not a bad light. My old Roberts had the same arrangement. The light fitted nicely under my Carradice bar bag, lighting up the road nicely without dazzling me. The Smart lights go on our mountain bikes.