RE: Servo Reversers.... how do they work?
If your comfortable with opening the servo and soldering, a servo can be reveresed.
The Two motor leads are reversed, along with the "Outside" leads on the feedback potentiometer ( Variable resistor).
Not hard to do ... "IF" you are comfortable.
Some of the new servo can be reversed by using a programmer ... a little expensive if you are only doing one.
FMA Direst has a "Hand Adjustable" Servo that can be adjusted for reverse, center and end points just by moving the servo "by Hand".
It is digital and about $30.00 ... P/N DS 300BB ... check it out ... if it will work for you, You will have another servo for the price of a reverser.
Good Luck !