Do these come with reflectors?
The shimano website specifies the SM-PD40 reflector set, which does not appear to be available separately?... http://www.shimano.com.au/media/techdocs/content/cycle/SI/Pedals/SM-PD40/SI-PD40C-ENG_v1_m56577569830606548.pdf
If you can't find reflectors for them then have a look at your cranks. If they're got square edges then buy some reflective tape and use a craft knife to cut it to fit. I used a white 3M A4 sheet bought from Wiggle and the result was very fine: the movement of the cranks really made the bike stand out, so it captured the best feature of the pedal reflectors.