Index of Plugins, found in the Plugins section of the main Calibre forum
Metadata SOURCE plugins are the TYPE
Characters ? Those are probably going to come from FAN site, which may or not, have a PI.
BUT there is a TOOL (PI),
Import List, where you might find a template OR you might use it to roll your own to scrape metadata from the targeted site
( I just looked, I don't see any easy way to Export or import additional templates
that would have been Handy for sharing)