SPY HINTS (SERIES 1)
SPY HINTS (SERIES 2)
Badges and stickers
There were at least two TV adverts for Double Agents sweets. The first is available from tv-ark.org.uk; click on the image below for a link to the page with the Double Agents commercial, plus many other old TV adverts.
The second commercial probably exists, but is not presently available; the below snapshot gives an idea of what it is like.