Save the money go to sportys.com click on pilot shop and there is a link there for the test prep and the study buddy. Or try faatest.com I have used this product and its great too , but I used the sportys one for my ppl and instrument tests and it was great.
PS echo mike, I am just 35 and had wet bulb thermometers in my school classrooms ! And dewpoint can and was in the past calculated from the wet bulb temperature , and surely you tell your students the significance of the dry bulb / dewpoint spread and its effects on what cloud or fog you can get. I too have taught the CAA syllabus up to ATPL level, and find it different, not arcane, it has a lot of useful info in it. ( ps I have taught Australian, Malaysian, South African, UK, JAA and FAA flight training in my 16 years in the industry and there all different, and have their pros and cons)