Passive Reflective Devices

Hi everybody

I would like to gather some information about a passive reflective device
which could be used to increase the visibility of a glider. It was
described to me as follows, during one of those typical launch point chats:

It takes the shape of small sphere, mounted just behind the canopy on
the turtle deck
The surface is covered with faceted mirrors, like a disco mirror ball

Apparently this little ball will sparkle as light from the sun is reflected
to the observer, thus making the glider more visible. Now my questions are
as follows:

Has anybody ever seen or heard of such a device?
If yes, how can one obtain these little do-hickeys, i.e. price and point
of sale.
Do they actually work?

Any other suggestions for passive reflective devices will also be
appreciated. Suggestions and thoughts on active devices, i.e. strobes will
also be handy.

Regards

Henk Stander