Sage M25W Resistor
The Sage Silicohm M25W is the shorter resistor on the Ion Arm of both the GB1 and GB2 Proton Packs. The resistor is mounted on the left side of the Ion Arm and has the 5/32" diameter yellow hose attached that goes from the resistor bottom lead to the Legris elbow.
These are readily available from many online sources.
Sage M50W Resistor
The Sage Silicohm M50W is the longer resistor on the Ion Arm, only visible on certain publicity shots of the GB1 Proton Packs (like the Omni cover pack). It was once believed that the Sage was used in GB1 and the Dale in GB2, but evidence seems to confirm that the Dale was used in both movies.
The resistor is mounted on the right of the Ion Arm and has 1/4" diameter blue hose attached to both leads. The top hose goes to the Clippard elbow on top of the Ion Arm, and the bottom hose goes to the PPD.
These are also readily available from many online sources.