I need information about tours to Lhasa for foreigners living in China.

My name is Tim and I am an American living in Zhuhai China. I understand I have to receive permission to travel to Tibet and I have been told I must be in a group of other foreigners as large as 10 to go. Can you help me with this since I do not know many foreigners here and would like to visit Tibet. I teach school so my time is rather limited. I was hoping to get a chance to go at the end of August sometime between the 24 and 30. I am most interested in seeing Potala Palace and Mount Everest.