This repo contains re-created versions of Classic Mac icons. I've done my best to make them pixel-perfect replicas, and of a consistent size, but if you spot any errors, please let me know.
The SVG files allow you to blow these up to any size you like without loss of quality. PNG files are also provided for convenience, since SVGs aren't the easiest for everyone to deal with. The PNGs are suitable for reasonably-sized stickers, if you so desire.
For scale, the alert icon sticker in the above image is 2 inches by 2 inches, which is a pretty good size for sticking on a laptop. :)
Enjoy!