What are some proven PLR eBook products that can support sales of around 500 units?

I'm responsible to manage the setup of a new info product marketing intiative to prove the model and potential ROI to my investors. They'd like to establish an ROI formula based on the sales of an eBook within any specific niche of my choosing. They're providing sufficient investment to fund the setup and paid traffic strategy of a pilot program. For the 60-day trial, they want me to leverage a PLR product rather than create something from scratch. Would you happen to know of a great PLR product that has proven success/traction within any particular niche? Obviously it needs to have sufficient capacity to scale for sales of around 500 units. Price point of $7-$9. Appreciate any…