That was quite the overreaction given the original question and replies. Unless I'm missing something on this thread or elsewhere, I see no need in bashing and berating the entire chasing community. I do wish Mr. Dean a speedy and as smooth as possible recovery. Cancer sucks.
My answer to the original question is based on my own personal experience and is in no way saying Mr. Dean's tour is subpar or should not be considered. This is just information for future reference in case there is trouble finding an open tour or scheduling conflicts. Early on in my meteorological studies and chasing career, I went on a tour in 2012 through College of DuPage:
http://weather.cod.edu/chasing/index.php?load=home
It was reasonably priced compared to what I've seen from other tours, and was one of the best chasing experiences my colleagues and I have ever had. They currently offer 5 10-day trips a year and have been doing tours for nearly 30 years.
Silver Lining Tours is another good one, which has already been mentioned. I have a friend who is a driver for them this year, and I believe he said that 2018 is already full, but that can always change.