Welcome to IndieTalk's Screenwriting forum. I'm sure you'll get several offers to write. This forum is typically populated by writers, so we don't typically "refer out".

There are a variety of writers on this forum--writer/directors, award-winning screenwriters, writing consultants/script doctors, producers, new writers, etc. Are you looking for a local writer or can they work remotely? We have writers from around the world who contribute. What you may wish to do is describe the nature of the project--genre, turnaround time, nature of project (student, lo/no budget, SAG), etc.
There is also a marketing services forum (Classified Ads) where you can request services. IndieTalk members are discouraged from advertising their services in the discussion forums. Some here have worked as script consultants with production companies though many new writers are looking for opportunities to obtain writing credits. Are you open to new writers who may be willing to write for credit?
I know you are asking for a referral for such services. As you consider services, here are some items to keep in mind. In evaluating any writer, you will want to request a writing sample. You might also request a quick write-up of the first five pages from your logline to evaluate as a writing sample. If hiring a writer/director, you can often view a clip of their work in addition to the script. Understand that screenwriting a feature often occurs in three phases--initial draft, the revised draft based on feedback and a final polish. Depending on the terms of the contract, you may get a couple additional revisions for free. While ghostwriting is typically work-for-hire so you retain all copyright and can retain credits, there is sometimes an advantage to share credit. This is especially true with a series.
A series often requires the development of several episodes, season arc and a bible. Unlike a feature, there is an ongoing commitment. A series will often require additional writers if the series takes off. Having the writer on board helps provide story continuity needed through your first season and forward.
Wishing you continued success as you move forward with your project.