Hi Abhi - I’d recruit from ex-journalists and fiction writers. There’s a ton of folks in those worlds struggling and out of work, but they don’t often position themselves or pursue more technical and content-marketing sorts of roles. The other thing I’d do is make sure your requests on topics and focus aren’t so boring and stale as to drive people away. Many marketers think they need to write on certain topics for SEO or keyword matching… Let your writers go beyond that stuff, be creative, be inventive, choose their own (relevant) topics, and you’ll attract far better candidates.
And yes! This is definitely something you can outsource. There’s loads of great copywriting firms and contractors out there, and almost all provide samples you can read and determine fit from.