It looks like the reason that FIRST went with the new sticks is that CH Products has discontinued the Flightstick. However, you can still buy the Flightstick Pro (the 4 button version of the Flightstick) for around $15 from places like
PC Connection. I can't personally vouch that the quality of the Flightstick Pro is the same as the Flightstick, but it is ambidextrous and has been well reviewed.
For those of you who really want the old 2-button Flightstick, you can buy them for $30 from
FlightSim Central.