I need an expression pedal for my Axe Fx Standard. I want one with a momentary switch (like the newer Whammy DT pedal).

Does a pedal like this exist?

Thank you!
I am not sure that such thing exists mate. It's kind of a "whammy-only" gimmick.
Can't you assign a seperate momentary switch to use as the DT momentary function the Whammy DT has and then use a "normal" expression pedal for the actual whammy? On the DT, the momentary switch only works for the DT-section of the pedal, so that should give you the same result.

To put it more clear, maybe:
Use an expression pedal for all the "regular" whammy stuff.
Use a separate momentary switch with some sort of pitch shifter.