The POTs on the Sticks are 10k, and you'll need 2 Resistors per POT to replace it. Ya can use any value from 4.7k up really, so long as ya keep the values the same for both Resistors. I use 10k, just easier to get a hold of.
An alternative to replacing the Stick with Resistors is to leave the POTs installed, remove the rest, and lock them off in the center position with some hot glue or something. This may also need to be done if after installing the Resistors ya notice it 'drifts' to one side or the other, some controllers are just really picky on those Analog lines or ya may need to try another set of Resistors as the tolerance of them may be off enough to cause it to drift.