Where can you rent a unicorn on Horseisle?

You must have 75% quest points, and then you have to go to the Cloud Isles. On one of the medium-sized clouds(the same one that has Aladdin's Castle), there will be two identical castles, one above the other. One is a Pegasus rental, the other a Unicorn rental. Both cost $1,000,000 for a two-hour rental. Once your rental is up, you are transported back to the rental store.