Heya and welcome here. I do not know which one offers the most features or is more accurate for the CAS, but the Classpad can take several minutes to perform certain equations, while every other model can do it in a few seconds. Also, HP calculators have long been popular towards enginers over here. The HP Prime also has more memory than the ClassPad, a rechargeable battery and in some countries it is cheaper.

In other words I would suggest the HP Prime.

I am unsure, but I recently bought one from the Canadian division of Staples (which is an American company). I wouldn't be surprised if some American retailers had it.


EDIT: Casio website has it: http://www.shopcasio.com/product/43384 but it's available via backorder.