Getting a single freelancer to win massively here is hit and miss — I would say 90% of the best creative talent are either in agency or high-growth tech startups.

You could try Upwork? At least there's some ratings there and some examples of writing. You need an excellent copywriter and someone who can also put together a visual moodboard.

If you'd like your campaign to extend into video or crowdfunding, check out some of our work: https://vidico.com or a specific case study example from one of our video productions: https://vidico.com/case-studies/koala-video/