Yes, there are. However, you'd have to be creative to mount a rear rack on the Mini due to the hinged rear triangle (for the rear suspension). The rear triangle will move relative to the frame when going over bumps.

I've seen some creative solutions to this, I just can't remember which post. Someone used a "flexible" attachment to the seatpost, while bolting the rear rack on. I hope that person will respond to this thread and explain what they did.