There is NO reason in the world to use "herewith" (which I know as a single word, not a hyphen). It's overly formal and doesn't add any meaning.
"Attached is..." is a very, very common way to say this, although "Please find attached the quote you requested..." is also very common and a bit more polite.
May I also suggest something like "Thank you for your inquiry regarding... The requested information is attached."