Take a look at some of these options:
https://www.etrailer.com/Hitch-Accessories/Lets-Go-Aero/63232.html
https://www.etrailer.com/Hitch-Accessories/Brophy/RSCP.html
https://www.etrailer.com/Hitch-Accessories/Roadmaster/RM-061.html
I am using one to stabilize my rear mounted bike rack with...