I'm completely new to guitars and guitar accessories.
I read several articles on (everything, but this question pertains to) strings, and it strikes me that one might want to try a set of strings with certain characteristics. Initially I figured this wouldn't be too much of a struggle, but in my quest to find a set of light/extra light (10s) acoustic flatwound coated strings, I've been unsuccessful.
This has been made more difficult by the lack of useful filtering functionality on websites that sell strings, so even though store A might have 3800 different sets of strings, there's not a good way to find what you want even if it exists.
It seems like the done thing might instead be to choose strings based on only one characteristic, and then stick with a specific brand or what have you.
Originally this question was specifically "where can I find acoustic flatwound coated 10s?" But I figure a more useful and broad question is the one asked in the title. With a comprehensive database of string brand-model combinations, and all their characteristics, one could easily look for what they want, then search for e.g. "D'Addario EFT15" and not have to deal with the issues I encountered.