I don't believe that Hyundai are willing to put their cars available for buying or renting. They said it couple of years ago that they don't allow that. Except old gen cars.

Toyota I think is more open for that but only for a selected drivers not anyone.

M-Sport is free and are happy of anyone driving their cars, so easiest solution is their cars.

Citroen, nah. Why would anyone bother if the car is so bad that even the best drivers of the world left them. Only Ostberg could get them a go, but I think he will rather look elsewhere now.