This site:
http://www.stclaire.com/safety_sign_builder/ssb-panel.php
enables you to design your own safety signs, using standard symbols,
in the size you want, and print them out on your own printer. It’s a
commercial concern, so maybe they’ll do an e-mail follow-up to try
to sell you their other services (which seem to be safety related),
but the sign making facility seems useful.
Kevin (NW England, UK)