The phrase "a third party vendor" is correct and usable in written English.
It is typically used in business or legal contexts to refer to an external company or individual that provides goods or services to another company.
Example: "We need to evaluate the contract with a third party vendor before proceeding with the project."
Alternatives: "an external supplier" or "a third-party provider".
Wired seems to think they have the scoop on the ultraportable that's being announced tomorrow from a third party vendor.
In other words: if a third party vendor ordered 500,000 units but only actually managed to sell 400,000 to end-users, it's still counted as 500,000 sales.
McDonald's is currently investigating the posts on the website, which were written by a third party vendor called Adam.
The plaintiffs in the litigation were employed by a third party vendor to another vendor to Schneider.
Thanks to the sharing economy, we now have the power to consume collaboratively, relying on the resources of one another, rather than a third party vendor.
"The costume was listed by a third party vendor and is in clear violation of our policy," a representative for Walmart told The Huffington Post via phone on Tuesday.
According to a statement from CFPB director Richard Cordray (you remember, he's the fellow the Party of No said, well, "No" to...), representatives working for a third-party vendor engaged in deceptive practices by hawking "Payment Protection" and "Credit Monitoring" products to consumers with low credit scores and low credit limits.
Each of the wireless providers has contracted with a third-party vendor to handle the processing of the request.
Documents on Yeshiva's Web site state that finalists for jobs at the university are subjected to a criminal history check by a "third-party vendor".
The regulators are investigating reports that the bank sold credit card customers, through a third-party vendor, the identity-theft protection with false promises.
Commercial Food Services Equipment, a third-party vendor in Chicago, lists a Thunderbird for sale on Amazon, but charges almost $2,600 for shipping.
