Don't bother; this device would not help you acclimate to altitude. Respiratory fatigue is not the limiting factor you will face (although it might feel like it
The breathlessness we sea-level folks experience when visiting the USAFA has to do with the reduced partial pressure of oxygen in the air due to a lower atmospheric pressure there. About the only way to adapt to this before going to altitude is to be exposed to either hypobaric conditions at sea level (read altitude chamber living - not practical) or to breath gas with a lowered oxygen content for a substantial portion of the day/night. There are actually "simulated altitude" tents that can be used for this...not as expensive as using a hypobaric chamber, but still expensive and IMHO not worth it for your endeavor.
My advice, get in the best shape you can and don't worry about it too much. Most of your class-mates will be sharing your misery. You should notice an improvement after a few days (acid-base shifts in the blood), although it will take a few months to completely acclimate (increased hemoglobin, red cell count, etc).
Good luck!
(Soaring Dad is a Physiologist (day job) - and a glider pilot (weekends))