You need these beads:

This is a lifetime supply and then some. I got it off Ebay for 2 quid.
Only two beads are needed:

Also needed are two German spec clothes pins (courtesy of Ebay.de, they cost pennies. Go to ebay.de and search for "Stecknadeln"):

Tamiya Clear is used as a glue:

Simply on the grounds that it sticks like ###### and will stay clear until long after the last archeologist is dead.
Glue the two beads onto the two pins with Tamiya clear like this:

Glue the pins with beads into the reflectors with Tamiya Clear like this:

After the above has dried, glue the lenses back to the reflectors with Tamiya Clear:

Cut the pins flush with the reflectors and glue the whole shebang to the model with - you guessed it - Tamiya clear.
The effect is very convincing: