What's stopping you from writing them yourself? Sounds a lot more fun to me than letting someone else handle it. You don't need to be a professional writer to write for your OCs, and it IS a hobby after all.
I agree with Duo. A big part of what makes OCs special is that they're something that you create on your own. I feel like outsourcing their creation to other people takes away that personal connection and robs them of their sentimental value. I'd suggest attempting to write their backstories yourself. If you're having trouble, perhaps take a look at official Pokémon characters, find what you like and put your own spins on the concepts you find. Even if you're not quite satisfied with what you come up with now, it will be an invaluable learning experience and help you to develop the skills needed to make better OCs in the future.
I agree with what they say however if you absolutely want i'll give you a draft for the hell of it but nothing more.