Hi there! I purchase quite a bit of PLR, but tend to focus on content about digital marketing and online business rather than physical therapy and sports medicine. My go-to sources are AllPrivateLabelContent.com, ToolsforMotivation.com, BestQualityPLR.com, CoachGlue.com and ContentSparks.com.
Tiffany Lambert's PLRMinimart.com has a bunch of health and wellness content at very good prices, and she's a stand-up ethical online seller. Another one I know and trust in the health/wellness field is JR Lang at InternetSlayers.com.
Hope this helps you! Best of luck.
Not sure if this is what you're looking for, but a friend of mine started this: http://bemaven.co/
Here's a summary from their site:
We brainstorm, write, and publish world-class stories on your behalf. We turn your ideas into powerful thought pieces.
Our tech platform works in the background to quietly deliver remarkably pleasing results. Building your personal brand is our worry, not yours.
We work with you to develop a consistent voice that becomes the cornerstone of your personal brand — by combining software and services.
Our platform combines new school data analytics and old school media partnerships. It’s the art and science of getting your voice heard.
What do you need? I can create detailed copy on any subject.
Please be careful with content that's not written for you specifically.
I've had clients in the past who've subscribed to a service that would provide blog post text to multiple companies, meaning the same post could appear on dozens of websites in the same industry at the same time.
Apparently, the once feared "duplicate content" penalty on Google is not as fearsome as some people previously claimed. Your website probably won't be delisted or punished for publishing something already published word-for-word somewhere else, especially if it's not in your geographic area. But neither will generic content bring your website much SEO benefit either.
The key phrase in your question is "high quality," and most private label content I've seen sounds canned. Even if your customers don't figure it out right away, they'll sense that you didn't create the content just for them, which is what Web visitors increasingly expect these days.
If you can afford it, better than buying canned content from a vendor is to hire a writer to create content just for you. And if budget is an issue, then go for quality rather than quantity. Five blog posts ghostwritten from your POV and with at least some of your special touches will be more valuable than a series of a dozen generic texts that could go up on any physical therapy or sports medicine site online.