The best replacement would probably be Hall sensors though I'm uncertain what effect FF would have on their functionality.
Here's what I found regarding ratings:
Force 3D/Strike Force 3D
DigiKey: 963223-KIT-ND FORCE 3D
DigiKey: 963191-KIT-ND STRIKE FORCE 3D
RES,VAR,100K,50DEG,+/-10%,PLAS 3 X, Y, Twist
RES,VAR,100K,70DEG,+/-10%,PLAS 1 Throttle
Extreme Digital 3D
DigiKey: 963193-KIT-ND EXTREME DIGITAL 3D
RES,VAR,100K,50DEG,+/-10%,PLAS 1 Twist
RES,VAR,100K,70DEG,+/-10%,PLAS 1 Throttle
RES,VAR,100K,50DEG,+/-10%,PLAS 2 X, Y
and straight from the horse's orifice - DigiKey