I have been collecting a few stickers over the years and I wanted to have a backup if I ever need to reproduce some of them ..... any idea what the best way is to do this?

Most importantly: Scan them at 100% scale, so that when ever you return to them in future you know that they are exact dimensionally.

2) scan them at 300 dpi or higher, thats about the quality of a good photograph, and its good enough quality to pick up any detailed parts (eg: colour blends, typographic registration etc.)

3) Do not then apply jpeg compression when saving. ie: do not save them as jpeg format or if saving them as an .eps file apply jpeg compression.
(Save them as .eps maximum quality)

4) Try to get the colours as exact as you can, by either adjusting the brightnes & contrast or colour curves.

5) If they are printed onto chrome try putting a sheet of baking or greesproof paper over them whilst scanning; this will reduce the glare.

In short you'll have to get them as exact as possible now whilst you still have the originals to work from.

Hope that helps