There are 2 different onboard PPK products that I have found.
The LOKI PPK system from Vertical Aspect derived from Robota LLC, both of these companies are Texas based. Integrated onto the P4P and Inspire 2 drones. http://www.robota.us/about/
Vertical Aspect Exclusive Texas Dealer for Robota Eclipse fixed wing mapping platform
I am investigating if this Emlid ground transmitter will work with the Vertical Aspect Loki receiver for a base station corrections transmitter. Emlid Reach RS — RTK GNSS receiver with an app as a controller
And this one... UAV Geomatics - UAV Geomatics